42 CFR 403.750 - Estimate of expenditures and adjustments.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 42 Public Health 2 2011-10-01 2011-10-01 false Estimate of expenditures and adjustments. 403.750 Section 403.750 Public Health CENTERS FOR MEDICARE & MEDICAID SERVICES, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL PROVISIONS SPECIAL PROGRAMS AND PROJECTS Religious Nonmedical Health Care Institutions...

42 CFR 403.750 - Estimate of expenditures and adjustments.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 42 Public Health 2 2014-10-01 2014-10-01 false Estimate of expenditures and adjustments. 403.750 Section 403.750 Public Health CENTERS FOR MEDICARE & MEDICAID SERVICES, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL PROVISIONS SPECIAL PROGRAMS AND PROJECTS Religious Nonmedical Health Care Institutions...

42 CFR 403.750 - Estimate of expenditures and adjustments.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 42 Public Health 2 2010-10-01 2010-10-01 false Estimate of expenditures and adjustments. 403.750 Section 403.750 Public Health CENTERS FOR MEDICARE & MEDICAID SERVICES, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL PROVISIONS SPECIAL PROGRAMS AND PROJECTS Religious Nonmedical Health Care Institutions...

42 CFR 403.750 - Estimate of expenditures and adjustments.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 42 Public Health 2 2012-10-01 2012-10-01 false Estimate of expenditures and adjustments. 403.750 Section 403.750 Public Health CENTERS FOR MEDICARE & MEDICAID SERVICES, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL PROVISIONS SPECIAL PROGRAMS AND PROJECTS Religious Nonmedical Health Care Institutions...

42 CFR 403.750 - Estimate of expenditures and adjustments.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 42 Public Health 2 2013-10-01 2013-10-01 false Estimate of expenditures and adjustments. 403.750 Section 403.750 Public Health CENTERS FOR MEDICARE & MEDICAID SERVICES, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL PROVISIONS SPECIAL PROGRAMS AND PROJECTS Religious Nonmedical Health Care Institutions...

Estimates of over-diagnosis of breast cancer due to population-based mammography screening in South Australia after adjustment for lead time effects.

PubMed

Beckmann, Kerri; Duffy, Stephen W; Lynch, John; Hiller, Janet; Farshid, Gelareh; Roder, David

2015-09-01

To estimate over-diagnosis due to population-based mammography screening using a lead time adjustment approach, with lead time measures based on symptomatic cancers only. Women aged 40-84 in 1989-2009 in South Australia eligible for mammography screening. Numbers of observed and expected breast cancer cases were compared, after adjustment for lead time. Lead time effects were modelled using age-specific estimates of lead time (derived from interval cancer rates and predicted background incidence, using maximum likelihood methods) and screening sensitivity, projected background breast cancer incidence rates (in the absence of screening), and proportions screened, by age and calendar year. Lead time estimates were 12, 26, 43 and 53 months, for women aged 40-49, 50-59, 60-69 and 70-79 respectively. Background incidence rates were estimated to have increased by 0.9% and 1.2% per year for invasive and all breast cancer. Over-diagnosis among women aged 40-84 was estimated at 7.9% (0.1-12.0%) for invasive cases and 12.0% (5.7-15.4%) when including ductal carcinoma in-situ (DCIS). We estimated 8% over-diagnosis for invasive breast cancer and 12% inclusive of DCIS cancers due to mammography screening among women aged 40-84. These estimates may overstate the extent of over-diagnosis if the increasing prevalence of breast cancer risk factors has led to higher background incidence than projected. © The Author(s) 2015.

Gauge-adjusted rainfall estimates from commercial microwave links

NASA Astrophysics Data System (ADS)

Fencl, Martin; Dohnal, Michal; Rieckermann, Jörg; Bareš, Vojtěch

2017-01-01

Increasing urbanization makes it more and more important to have accurate stormwater runoff predictions, especially with potentially severe weather and climatic changes on the horizon. Such stormwater predictions in turn require reliable rainfall information. Especially for urban centres, the problem is that the spatial and temporal resolution of rainfall observations should be substantially higher than commonly provided by weather services with their standard rainfall monitoring networks. Commercial microwave links (CMLs) are non-traditional sensors, which have been proposed about a decade ago as a promising solution. CMLs are line-of-sight radio connections widely used by operators of mobile telecommunication networks. They are typically very dense in urban areas and can provide path-integrated rainfall observations at sub-minute resolution. Unfortunately, quantitative precipitation estimates (QPEs) from CMLs are often highly biased due to several epistemic uncertainties, which significantly limit their usability. In this manuscript we therefore suggest a novel method to reduce this bias by adjusting QPEs to existing rain gauges. The method has been specifically designed to produce reliable results even with comparably distant rain gauges or cumulative observations. This eliminates the need to install reference gauges and makes it possible to work with existing information. First, the method is tested on data from a dedicated experiment, where a CML has been specifically set up for rainfall monitoring experiments, as well as operational CMLs from an existing cellular network. Second, we assess the performance for several experimental layouts of ground truth from rain gauges (RGs) with different spatial and temporal resolutions. The results suggest that CMLs adjusted by RGs with a temporal aggregation of up to 1 h (i) provide precise high-resolution QPEs (relative error < 7 %, Nash-Sutcliffe efficiency coefficient > 0.75) and (ii) that the

Bias-adjusted satellite-based rainfall estimates for predicting floods: Narayani Basin

USGS Publications Warehouse

Artan, Guleid A.; Tokar, S.A.; Gautam, D.K.; Bajracharya, S.R.; Shrestha, M.S.

2011-01-01

In Nepal, as the spatial distribution of rain gauges is not sufficient to provide detailed perspective on the highly varied spatial nature of rainfall, satellite-based rainfall estimates provides the opportunity for timely estimation. This paper presents the flood prediction of Narayani Basin at the Devghat hydrometric station (32 000 km2) using bias-adjusted satellite rainfall estimates and the Geospatial Stream Flow Model (GeoSFM), a spatially distributed, physically based hydrologic model. The GeoSFM with gridded gauge observed rainfall inputs using kriging interpolation from 2003 was used for calibration and 2004 for validation to simulate stream flow with both having a Nash Sutcliff Efficiency of above 0.7. With the National Oceanic and Atmospheric Administration Climate Prediction Centre's rainfall estimates (CPC_RFE2.0), using the same calibrated parameters, for 2003 the model performance deteriorated but improved after recalibration with CPC_RFE2.0 indicating the need to recalibrate the model with satellite-based rainfall estimates. Adjusting the CPC_RFE2.0 by a seasonal, monthly and 7-day moving average ratio, improvement in model performance was achieved. Furthermore, a new gauge-satellite merged rainfall estimates obtained from ingestion of local rain gauge data resulted in significant improvement in flood predictability. The results indicate the applicability of satellite-based rainfall estimates in flood prediction with appropriate bias correction.

NDVI saturation adjustment: a new approach for improving cropland performance estimates in the Greater Platte River Basin, USA

USGS Publications Warehouse

Gu, Yingxin; Wylie, Bruce K.; Howard, Daniel M.; Phuyal, Khem P.; Ji, Lei

2013-01-01

In this study, we developed a new approach that adjusted normalized difference vegetation index (NDVI) pixel values that were near saturation to better characterize the cropland performance (CP) in the Greater Platte River Basin (GPRB), USA. The relationship between NDVI and the ratio vegetation index (RVI) at high NDVI values was investigated, and an empirical equation for estimating saturation-adjusted NDVI (NDVIsat_adjust) based on RVI was developed. A 10-year (2000–2009) NDVIsat_adjust data set was developed using 250-m 7-day composite historical eMODIS (expedited Moderate Resolution Imaging Spectroradiometer) NDVI data. The growing season averaged NDVI (GSN), which is a proxy for ecosystem performance, was estimated and long-term NDVI non-saturation- and saturation-adjusted cropland performance (CPnon_sat_adjust, CPsat_adjust) maps were produced over the GPRB. The final CP maps were validated using National Agricultural Statistics Service (NASS) crop yield data. The relationship between CPsat_adjust and the NASS average corn yield data (r = 0.78, 113 samples) is stronger than the relationship between CPnon_sat_adjust and the NASS average corn yield data (r = 0.67, 113 samples), indicating that the new CPsat_adjust map reduces the NDVI saturation effects and is in good agreement with the corn yield ground observations. Results demonstrate that the NDVI saturation adjustment approach improves the quality of the original GSN map and better depicts the actual vegetation conditions of the GPRB cropland systems.

The effect of accuracy motivation on anchoring and adjustment: do people adjust from provided anchors?

PubMed

Simmons, Joseph P; LeBoeuf, Robyn A; Nelson, Leif D

2010-12-01

Increasing accuracy motivation (e.g., by providing monetary incentives for accuracy) often fails to increase adjustment away from provided anchors, a result that has led researchers to conclude that people do not effortfully adjust away from such anchors. We challenge this conclusion. First, we show that people are typically uncertain about which way to adjust from provided anchors and that this uncertainty often causes people to believe that they have initially adjusted too far away from such anchors (Studies 1a and 1b). Then, we show that although accuracy motivation fails to increase the gap between anchors and final estimates when people are uncertain about the direction of adjustment, accuracy motivation does increase anchor-estimate gaps when people are certain about the direction of adjustment, and that this is true regardless of whether the anchors are provided or self-generated (Studies 2, 3a, 3b, and 5). These results suggest that people do effortfully adjust away from provided anchors but that uncertainty about the direction of adjustment makes that adjustment harder to detect than previously assumed. This conclusion has important theoretical implications, suggesting that currently emphasized distinctions between anchor types (self-generated vs. provided) are not fundamental and that ostensibly competing theories of anchoring (selective accessibility and anchoring-and-adjustment) are complementary. PsycINFO Database Record (c) 2010 APA, all rights reserved.

Estimating restricted mean treatment effects with stacked survival models

PubMed Central

Wey, Andrew; Vock, David M.; Connett, John; Rudser, Kyle

2016-01-01

The difference in restricted mean survival times between two groups is a clinically relevant summary measure. With observational data, there may be imbalances in confounding variables between the two groups. One approach to account for such imbalances is estimating a covariate-adjusted restricted mean difference by modeling the covariate-adjusted survival distribution, and then marginalizing over the covariate distribution. Since the estimator for the restricted mean difference is defined by the estimator for the covariate-adjusted survival distribution, it is natural to expect that a better estimator of the covariate-adjusted survival distribution is associated with a better estimator of the restricted mean difference. We therefore propose estimating restricted mean differences with stacked survival models. Stacked survival models estimate a weighted average of several survival models by minimizing predicted error. By including a range of parametric, semi-parametric, and non-parametric models, stacked survival models can robustly estimate a covariate-adjusted survival distribution and, therefore, the restricted mean treatment effect in a wide range of scenarios. We demonstrate through a simulation study that better performance of the covariate-adjusted survival distribution often leads to better mean-squared error of the restricted mean difference although there are notable exceptions. In addition, we demonstrate that the proposed estimator can perform nearly as well as Cox regression when the proportional hazards assumption is satisfied and significantly better when proportional hazards is violated. Finally, the proposed estimator is illustrated with data from the United Network for Organ Sharing to evaluate post-lung transplant survival between large and small-volume centers. PMID:26934835

A risk adjustment approach to estimating the burden of skin disease in the United States.

PubMed

Lim, Henry W; Collins, Scott A B; Resneck, Jack S; Bolognia, Jean; Hodge, Julie A; Rohrer, Thomas A; Van Beek, Marta J; Margolis, David J; Sober, Arthur J; Weinstock, Martin A; Nerenz, David R; Begolka, Wendy Smith; Moyano, Jose V

2018-01-01

Direct insurance claims tabulation and risk adjustment statistical methods can be used to estimate health care costs associated with various diseases. In this third manuscript derived from the new national Burden of Skin Disease Report from the American Academy of Dermatology, a risk adjustment method that was based on modeling the average annual costs of individuals with or without specific diseases, and specifically tailored for 24 skin disease categories, was used to estimate the economic burden of skin disease. The results were compared with the claims tabulation method used in the first 2 parts of this project. The risk adjustment method estimated the direct health care costs of skin diseases to be $46 billion in 2013, approximately $15 billion less than estimates using claims tabulation. For individual skin diseases, the risk adjustment cost estimates ranged from 11% to 297% of those obtained using claims tabulation for the 10 most costly skin disease categories. Although either method may be used for purposes of estimating the costs of skin disease, the choice of method will affect the end result. These findings serve as an important reference for future discussions about the method chosen in health care payment models to estimate both the cost of skin disease and the potential cost impact of care changes. Copyright © 2017 American Academy of Dermatology, Inc. Published by Elsevier Inc. All rights reserved.

Bias-adjusted satellite-based rainfall estimates for predicting floods: Narayani Basin

USGS Publications Warehouse

Shrestha, M.S.; Artan, G.A.; Bajracharya, S.R.; Gautam, D.K.; Tokar, S.A.

2011-01-01

In Nepal, as the spatial distribution of rain gauges is not sufficient to provide detailed perspective on the highly varied spatial nature of rainfall, satellite-based rainfall estimates provides the opportunity for timely estimation. This paper presents the flood prediction of Narayani Basin at the Devghat hydrometric station (32000km2) using bias-adjusted satellite rainfall estimates and the Geospatial Stream Flow Model (GeoSFM), a spatially distributed, physically based hydrologic model. The GeoSFM with gridded gauge observed rainfall inputs using kriging interpolation from 2003 was used for calibration and 2004 for validation to simulate stream flow with both having a Nash Sutcliff Efficiency of above 0.7. With the National Oceanic and Atmospheric Administration Climate Prediction Centre's rainfall estimates (CPC-RFE2.0), using the same calibrated parameters, for 2003 the model performance deteriorated but improved after recalibration with CPC-RFE2.0 indicating the need to recalibrate the model with satellite-based rainfall estimates. Adjusting the CPC-RFE2.0 by a seasonal, monthly and 7-day moving average ratio, improvement in model performance was achieved. Furthermore, a new gauge-satellite merged rainfall estimates obtained from ingestion of local rain gauge data resulted in significant improvement in flood predictability. The results indicate the applicability of satellite-based rainfall estimates in flood prediction with appropriate bias correction. ?? 2011 The Authors. Journal of Flood Risk Management ?? 2011 The Chartered Institution of Water and Environmental Management.

Adjusting for the Confounding Effects of Treatment Switching-The BREAK-3 Trial: Dabrafenib Versus Dacarbazine.

PubMed

Latimer, Nicholas R; Abrams, Keith R; Amonkar, Mayur M; Stapelkamp, Ceilidh; Swann, R Suzanne

2015-07-01

Patients with previously untreated BRAF V600E mutation-positive melanoma in BREAK-3 showed a median overall survival (OS) of 18.2 months for dabrafenib versus 15.6 months for dacarbazine (hazard ratio [HR], 0.76; 95% confidence interval, 0.48-1.21). Because patients receiving dacarbazine were allowed to switch to dabrafenib at disease progression, we attempted to adjust for the confounding effects on OS. Rank preserving structural failure time models (RPSFTMs) and the iterative parameter estimation (IPE) algorithm were used. Two analyses, "treatment group" (assumes treatment effect could continue until death) and "on-treatment observed" (assumes treatment effect disappears with discontinuation), were used to test the assumptions around the durability of the treatment effect. A total of 36 of 63 patients (57%) receiving dacarbazine switched to dabrafenib. The adjusted OS HRs ranged from 0.50 to 0.55, depending on the analysis. The RPSFTM and IPE "treatment group" and "on-treatment observed" analyses performed similarly well. RPSFTM and IPE analyses resulted in point estimates for the OS HR that indicate a substantial increase in the treatment effect compared with the unadjusted OS HR of 0.76. The results are uncertain because of the assumptions associated with the adjustment methods. The confidence intervals continued to cross 1.00; thus, the adjusted estimates did not provide statistically significant evidence of a treatment benefit on survival. However, it is clear that a standard intention-to-treat analysis will be confounded in the presence of treatment switching-a reliance on unadjusted analyses could lead to inappropriate practice. Adjustment analyses provide useful additional information on the estimated treatment effects to inform decision making. Treatment switching is common in oncology trials, and the implications of this for the interpretation of the clinical effectiveness and cost-effectiveness of the novel treatment are important to consider. If

Adjusting for the Confounding Effects of Treatment Switching—The BREAK-3 Trial: Dabrafenib Versus Dacarbazine

PubMed Central

Abrams, Keith R.; Amonkar, Mayur M.; Stapelkamp, Ceilidh; Swann, R. Suzanne

2015-01-01

Background. Patients with previously untreated BRAF V600E mutation-positive melanoma in BREAK-3 showed a median overall survival (OS) of 18.2 months for dabrafenib versus 15.6 months for dacarbazine (hazard ratio [HR], 0.76; 95% confidence interval, 0.48–1.21). Because patients receiving dacarbazine were allowed to switch to dabrafenib at disease progression, we attempted to adjust for the confounding effects on OS. Materials and Methods. Rank preserving structural failure time models (RPSFTMs) and the iterative parameter estimation (IPE) algorithm were used. Two analyses, “treatment group” (assumes treatment effect could continue until death) and “on-treatment observed” (assumes treatment effect disappears with discontinuation), were used to test the assumptions around the durability of the treatment effect. Results. A total of 36 of 63 patients (57%) receiving dacarbazine switched to dabrafenib. The adjusted OS HRs ranged from 0.50 to 0.55, depending on the analysis. The RPSFTM and IPE “treatment group” and “on-treatment observed” analyses performed similarly well. Conclusion. RPSFTM and IPE analyses resulted in point estimates for the OS HR that indicate a substantial increase in the treatment effect compared with the unadjusted OS HR of 0.76. The results are uncertain because of the assumptions associated with the adjustment methods. The confidence intervals continued to cross 1.00; thus, the adjusted estimates did not provide statistically significant evidence of a treatment benefit on survival. However, it is clear that a standard intention-to-treat analysis will be confounded in the presence of treatment switching—a reliance on unadjusted analyses could lead to inappropriate practice. Adjustment analyses provide useful additional information on the estimated treatment effects to inform decision making. Implications for Practice: Treatment switching is common in oncology trials, and the implications of this for the interpretation of the

Adjusting survival estimates for premature transmitter failure: A case study from the Sacramento-San Joaquin Delta

USGS Publications Warehouse

Holbrook, Christopher M.; Perry, Russell W.; Brandes, Patricia L.; Adams, Noah S.

2013-01-01

In telemetry studies, premature tag failure causes negative bias in fish survival estimates because tag failure is interpreted as fish mortality. We used mark-recapture modeling to adjust estimates of fish survival for a previous study where premature tag failure was documented. High rates of tag failure occurred during the Vernalis Adaptive Management Plan’s (VAMP) 2008 study to estimate survival of fall-run Chinook salmon (Oncorhynchus tshawytscha) during migration through the San Joaquin River and Sacramento-San Joaquin Delta, California. Due to a high rate of tag failure, the observed travel time distribution was likely negatively biased, resulting in an underestimate of tag survival probability in this study. Consequently, the bias-adjustment method resulted in only a small increase in estimated fish survival when the observed travel time distribution was used to estimate the probability of tag survival. Since the bias-adjustment failed to remove bias, we used historical travel time data and conducted a sensitivity analysis to examine how fish survival might have varied across a range of tag survival probabilities. Our analysis suggested that fish survival estimates were low (95% confidence bounds range from 0.052 to 0.227) over a wide range of plausible tag survival probabilities (0.48–1.00), and this finding is consistent with other studies in this system. When tags fail at a high rate, available methods to adjust for the bias may perform poorly. Our example highlights the importance of evaluating the tag life assumption during survival studies, and presents a simple framework for evaluating adjusted survival estimates when auxiliary travel time data are available.

Log Pearson type 3 quantile estimators with regional skew information and low outlier adjustments

USGS Publications Warehouse

Griffis, V.W.; Stedinger, Jery R.; Cohn, T.A.

2004-01-01

The recently developed expected moments algorithm (EMA) [Cohn et al., 1997] does as well as maximum likelihood estimations at estimating log‐Pearson type 3 (LP3) flood quantiles using systematic and historical flood information. Needed extensions include use of a regional skewness estimator and its precision to be consistent with Bulletin 17B. Another issue addressed by Bulletin 17B is the treatment of low outliers. A Monte Carlo study compares the performance of Bulletin 17B using the entire sample with and without regional skew with estimators that use regional skew and censor low outliers, including an extended EMA estimator, the conditional probability adjustment (CPA) from Bulletin 17B, and an estimator that uses probability plot regression (PPR) to compute substitute values for low outliers. Estimators that neglect regional skew information do much worse than estimators that use an informative regional skewness estimator. For LP3 data the low outlier rejection procedure generally results in no loss of overall accuracy, and the differences between the MSEs of the estimators that used an informative regional skew are generally modest in the skewness range of real interest. Samples contaminated to model actual flood data demonstrate that estimators which give special treatment to low outliers significantly outperform estimators that make no such adjustment.

Log Pearson type 3 quantile estimators with regional skew information and low outlier adjustments

NASA Astrophysics Data System (ADS)

Griffis, V. W.; Stedinger, J. R.; Cohn, T. A.

2004-07-01

The recently developed expected moments algorithm (EMA) [, 1997] does as well as maximum likelihood estimations at estimating log-Pearson type 3 (LP3) flood quantiles using systematic and historical flood information. Needed extensions include use of a regional skewness estimator and its precision to be consistent with Bulletin 17B. Another issue addressed by Bulletin 17B is the treatment of low outliers. A Monte Carlo study compares the performance of Bulletin 17B using the entire sample with and without regional skew with estimators that use regional skew and censor low outliers, including an extended EMA estimator, the conditional probability adjustment (CPA) from Bulletin 17B, and an estimator that uses probability plot regression (PPR) to compute substitute values for low outliers. Estimators that neglect regional skew information do much worse than estimators that use an informative regional skewness estimator. For LP3 data the low outlier rejection procedure generally results in no loss of overall accuracy, and the differences between the MSEs of the estimators that used an informative regional skew are generally modest in the skewness range of real interest. Samples contaminated to model actual flood data demonstrate that estimators which give special treatment to low outliers significantly outperform estimators that make no such adjustment.

Adjustment for survey non‐representativeness using record‐linkage: refined estimates of alcohol consumption by deprivation in Scotland

PubMed Central

Gorman, Emma; Leyland, Alastair H.; McCartney, Gerry; Katikireddi, Srinivasa Vittal; Rutherford, Lisa; Graham, Lesley; Robinson, Mark

2017-01-01

Abstract Background and aims Analytical approaches to addressing survey non‐participation bias typically use only demographic information to improve estimates. We applied a novel methodology which uses health information from data linkage to adjust for non‐representativeness. We illustrate the method by presenting adjusted alcohol consumption estimates for Scotland. Design Data on consenting respondents to the Scottish Health Surveys (SHeSs) 1995–2010 were linked confidentially to routinely collected hospital admission and mortality records. Synthetic observations representing non‐respondents were created using general population data. Multiple imputation was performed to compute adjusted alcohol estimates given a range of assumptions about the missing data. Adjusted estimates of mean weekly consumption were additionally calibrated to per‐capita alcohol sales data. Setting Scotland. Participants 13 936 male and 18 021 female respondents to the SHeSs 1995–2010, aged 20–64 years. Measurements Weekly alcohol consumption, non‐, binge‐ and problem‐drinking. Findings Initial adjustment for non‐response resulted in estimates of mean weekly consumption that were elevated by up to 17.8% [26.5 units (18.6–34.4)] compared with corrections based solely on socio‐demographic data [22.5 (17.7–27.3)]; other drinking behaviour estimates were little changed. Under more extreme assumptions the overall difference was up to 53%, and calibrating to sales estimates resulted in up to 88% difference. Increases were especially pronounced among males in deprived areas. Conclusions The use of routinely collected health data to reduce bias arising from survey non‐response resulted in higher alcohol consumption estimates among working‐age males in Scotland, with less impact for females. This new method of bias reduction can be generalized to other surveys to improve estimates of alternative harmful behaviours. PMID:28276110

Effect of time-activity adjustment on exposure assessment for traffic-related ultrafine particles

PubMed Central

Lane, Kevin J; Levy, Jonathan I; Scammell, Madeleine Kangsen; Patton, Allison P; Durant, John L; Mwamburi, Mkaya; Zamore, Wig; Brugge, Doug

2015-01-01

Exposures to ultrafine particles (<100 nm, estimated as particle number concentration, PNC) differ from ambient concentrations because of the spatial and temporal variability of both PNC and people. Our goal was to evaluate the influence of time-activity adjustment on exposure assignment and associations with blood biomarkers for a near-highway population. A regression model based on mobile monitoring and spatial and temporal variables was used to generate hourly ambient residential PNC for a full year for a subset of participants (n=140) in the Community Assessment of Freeway Exposure and Health study. We modified the ambient estimates for each hour using personal estimates of hourly time spent in five micro-environments (inside home, outside home, at work, commuting, other) as well as particle infiltration. Time-activity adjusted (TAA)-PNC values differed from residential ambient annual average (RAA)-PNC, with lower exposures predicted for participants who spent more time away from home. Employment status and distance to highway had a differential effect on TAA-PNC. We found associations of RAA-PNC with high sensitivity C-reactive protein and Interleukin-6, although exposure-response functions were non-monotonic. TAA-PNC associations had larger effect estimates and linear exposure-response functions. Our findings suggest that time-activity adjustment improves exposure assessment for air pollutants that vary greatly in space and time. PMID:25827314

Estimation of group means when adjusting for covariates in generalized linear models.

PubMed

Qu, Yongming; Luo, Junxiang

2015-01-01

Generalized linear models are commonly used to analyze categorical data such as binary, count, and ordinal outcomes. Adjusting for important prognostic factors or baseline covariates in generalized linear models may improve the estimation efficiency. The model-based mean for a treatment group produced by most software packages estimates the response at the mean covariate, not the mean response for this treatment group for the studied population. Although this is not an issue for linear models, the model-based group mean estimates in generalized linear models could be seriously biased for the true group means. We propose a new method to estimate the group mean consistently with the corresponding variance estimation. Simulation showed the proposed method produces an unbiased estimator for the group means and provided the correct coverage probability. The proposed method was applied to analyze hypoglycemia data from clinical trials in diabetes. Copyright © 2014 John Wiley & Sons, Ltd.

Using local multiplicity to improve effect estimation from a hypothesis-generating pharmacogenetics study.

PubMed

Zou, W; Ouyang, H

2016-02-01

We propose a multiple estimation adjustment (MEA) method to correct effect overestimation due to selection bias from a hypothesis-generating study (HGS) in pharmacogenetics. MEA uses a hierarchical Bayesian approach to model individual effect estimates from maximal likelihood estimation (MLE) in a region jointly and shrinks them toward the regional effect. Unlike many methods that model a fixed selection scheme, MEA capitalizes on local multiplicity independent of selection. We compared mean square errors (MSEs) in simulated HGSs from naive MLE, MEA and a conditional likelihood adjustment (CLA) method that model threshold selection bias. We observed that MEA effectively reduced MSE from MLE on null effects with or without selection, and had a clear advantage over CLA on extreme MLE estimates from null effects under lenient threshold selection in small samples, which are common among 'top' associations from a pharmacogenetics HGS.

15 CFR 6.5 - Effective date of adjustments.

Code of Federal Regulations, 2010 CFR

2010-01-01

... INFLATION ADJUSTMENTS § 6.5 Effective date of adjustments. The adjustments made by § 6.4 of this part, of... December 11, 2008, and before the effective date of any future inflation adjustment thereto made subsequent...

Using VS30 to Estimate Station ML Adjustments (dML)

NASA Astrophysics Data System (ADS)

Yong, A.; Herrick, J.; Cochran, E. S.; Andrews, J. R.; Yu, E.

2017-12-01

Currently, new seismic stations added to a regional seismic network cannot be used to calculate local or Richter magnitude (ML) until a revised region-wide amplitude decay function is developed. The new station must record a minimum number of local and regional events that meet specific amplitude requirements prior to re-calibration of the amplitude decay function. Therefore, there can be significant delay between when a new station starts contributing real-time waveform packets and when the data can be included in magnitude estimation. The station component adjustments (dML; Uhrhammer et al., 2011) are calculated after first inverting for a new regional amplitude decay function, constrained by the sum of dML for long-running stations. Here, we propose a method to calculate an initial dML using known or proxy values of seismic site conditions. For site conditions, we use the time-averaged shear-wave velocity (VS) of the upper 30 m (VS30). We solve for dML as described in Equation (1) by Uhrhammer et al. (2011): ML = log (A) - log A0 (r) + dML, where A is the maximum Wood and Anderson (1925) trace amplitude (mm), r is the distance (km), and dML is the station adjustment. Measured VS30 and estimated dML data are comprised of records from 887 horizontal components (east-west and north-south orientations) from 93 seismic monitoring stations in the California Integrated Seismic Network. VS30 values range from 202 m/s to 1464 m/s and dML range from -1.10 to 0.39. VS30 and dML exhibit a positive correlation coefficient (R = 0.72), indicating that as VS30 increases, dML increases. This implies that greater site amplification (i.e., lower VS30) results in smaller ML. When we restrict VS30 < 760 m/s to focus on dML at soft soil to soft rock sites, R increases to 0.80. In locations where measured VS30 data are unavailable, we evaluate the use of proxy-based VS30 estimates based on geology, topographic slope and terrain classification, as well as other hybridized methods

15 CFR 6.5 - Effective date of adjustments.

Code of Federal Regulations, 2011 CFR

2011-01-01

... Section 6.5 Commerce and Foreign Trade Office of the Secretary of Commerce CIVIL MONETARY PENALTY INFLATION ADJUSTMENTS § 6.5 Effective date of adjustments. The adjustments made by § 6.4 of this part, of... December 11, 2008, and before the effective date of any future inflation adjustment thereto made subsequent...

15 CFR 6.5 - Effective date of adjustments.

Code of Federal Regulations, 2013 CFR

2013-01-01

... Section 6.5 Commerce and Foreign Trade Office of the Secretary of Commerce CIVIL MONETARY PENALTY INFLATION ADJUSTMENTS § 6.5 Effective date of adjustments. The adjustments made by § 6.4 of this part, of... December 7, 2012, and before the effective date of any future inflation adjustment thereto made subsequent...

Doubly robust matching estimators for high dimensional confounding adjustment.

PubMed

Antonelli, Joseph; Cefalu, Matthew; Palmer, Nathan; Agniel, Denis

2018-05-11

Valid estimation of treatment effects from observational data requires proper control of confounding. If the number of covariates is large relative to the number of observations, then controlling for all available covariates is infeasible. In cases where a sparsity condition holds, variable selection or penalization can reduce the dimension of the covariate space in a manner that allows for valid estimation of treatment effects. In this article, we propose matching on both the estimated propensity score and the estimated prognostic scores when the number of covariates is large relative to the number of observations. We derive asymptotic results for the matching estimator and show that it is doubly robust in the sense that only one of the two score models need be correct to obtain a consistent estimator. We show via simulation its effectiveness in controlling for confounding and highlight its potential to address nonlinear confounding. Finally, we apply the proposed procedure to analyze the effect of gender on prescription opioid use using insurance claims data. © 2018, The International Biometric Society.

[Applying temporally-adjusted land use regression models to estimate ambient air pollution exposure during pregnancy].

PubMed

Zhang, Y J; Xue, F X; Bai, Z P

2017-03-06

The impact of maternal air pollution exposure on offspring health has received much attention. Precise and feasible exposure estimation is particularly important for clarifying exposure-response relationships and reducing heterogeneity among studies. Temporally-adjusted land use regression (LUR) models are exposure assessment methods developed in recent years that have the advantage of having high spatial-temporal resolution. Studies on the health effects of outdoor air pollution exposure during pregnancy have been increasingly carried out using this model. In China, research applying LUR models was done mostly at the model construction stage, and findings from related epidemiological studies were rarely reported. In this paper, the sources of heterogeneity and research progress of meta-analysis research on the associations between air pollution and adverse pregnancy outcomes were analyzed. The methods of the characteristics of temporally-adjusted LUR models were introduced. The current epidemiological studies on adverse pregnancy outcomes that applied this model were systematically summarized. Recommendations for the development and application of LUR models in China are presented. This will encourage the implementation of more valid exposure predictions during pregnancy in large-scale epidemiological studies on the health effects of air pollution in China.

Estimation of health effects of prenatal methylmercury exposure using structural equation models.

PubMed

Budtz-Jørgensen, Esben; Keiding, Niels; Grandjean, Philippe; Weihe, Pal

2002-10-14

Observational studies in epidemiology always involve concerns regarding validity, especially measurement error, confounding, missing data, and other problems that may affect the study outcomes. Widely used standard statistical techniques, such as multiple regression analysis, may to some extent adjust for these shortcomings. However, structural equations may incorporate most of these considerations, thereby providing overall adjusted estimations of associations. This approach was used in a large epidemiological data set from a prospective study of developmental methyl-mercury toxicity. Structural equation models were developed for assessment of the association between biomarkers of prenatal mercury exposure and neuropsychological test scores in 7 year old children. Eleven neurobehavioral outcomes were grouped into motor function and verbally mediated function. Adjustment for local dependence and item bias was necessary for a satisfactory fit of the model, but had little impact on the estimated mercury effects. The mercury effect on the two latent neurobehavioral functions was similar to the strongest effects seen for individual test scores of motor function and verbal skills. Adjustment for contaminant exposure to poly chlorinated biphenyls (PCBs) changed the estimates only marginally, but the mercury effect could be reduced to non-significance by assuming a large measurement error for the PCB biomarker. The structural equation analysis allows correction for measurement error in exposure variables, incorporation of multiple outcomes and incomplete cases. This approach therefore deserves to be applied more frequently in the analysis of complex epidemiological data sets.

Quantum metrology and estimation of Unruh effect

PubMed Central

Wang, Jieci; Tian, Zehua; Jing, Jiliang; Fan, Heng

2014-01-01

We study the quantum metrology for a pair of entangled Unruh-Dewitt detectors when one of them is accelerated and coupled to a massless scalar field. Comparing with previous schemes, our model requires only local interaction and avoids the use of cavities in the probe state preparation process. We show that the probe state preparation and the interaction between the accelerated detector and the external field have significant effects on the value of quantum Fisher information, correspondingly pose variable ultimate limit of precision in the estimation of Unruh effect. We find that the precision of the estimation can be improved by a larger effective coupling strength and a longer interaction time. Alternatively, the energy gap of the detector has a range that can provide us a better precision. Thus we may adjust those parameters and attain a higher precision in the estimation. We also find that an extremely high acceleration is not required in the quantum metrology process. PMID:25424772

Effective fiber for lactating dairy cows: a physically adjusted NDF (paNDF) system

USDA-ARS?s Scientific Manuscript database

Multiplying dietary NDF by particle size (PS) has been used as an estimate of physically effective fiber (peNDF). Our objectives were to: 1) compare the use of peNDF as dietary NDF × PS vs. use of individual NDF and PS descriptors in a physically adjusted NDF (paNDF) system when used with other fact...

Estimating regression to the mean and true effects of an intervention in a four-wave panel study.

PubMed

Gmel, Gerhard; Wicki, Matthias; Rehm, Jürgen; Heeb, Jean-Luc

2008-01-01

First, to analyse whether a taxation-related decrease in spirit prices had a similar effect on spirit consumption for low-, medium- and high-level drinkers. Secondly, as the relationship between baseline values and post-intervention changes is confounded with regression to the mean (RTM) effects, to apply different approaches for estimating the RTM effect and true change. Consumption of spirits and total alcohol consumption were analysed in a four-wave panel study (one pre-intervention and three post-intervention measurements) of 889 alcohol consumers sampled from the general population of Switzerland. Two correlational methods, one method quantitatively estimating the RTM effect and one growth curve approach based on hierarchical linear models (HLM), were used to estimate RTM effects among low-, medium- and high-level drinkers. Adjusted for RTM effects, high-level drinkers increased consumption more than lighter drinkers in the short term, but this was not a persisting effect. Changes in taxation affected mainly light and moderate drinkers in the long term. All methods concurred that RTM effects were present to a considerable degree, and methods quantifying the RTM effect or adjusting for it yielded similar estimates. Intervention studies have to consider RTM effects both in the study design and in the evaluation methods. Observed changes can be adjusted for RTM effects and true change can be estimated. The recommended method, particularly if the aim is to estimate change not only for the sample as a whole, but for groups of drinkers with different baseline consumption levels, is growth curve modelling. If reliability of measurement instruments cannot be increased, the incorporation of more than one pre-intervention measurement point may be a valuable adjustment of the study design.

Dynamically adjustable foot-ground contact model to estimate ground reaction force during walking and running.

PubMed

Jung, Yihwan; Jung, Moonki; Ryu, Jiseon; Yoon, Sukhoon; Park, Sang-Kyoon; Koo, Seungbum

2016-03-01

Human dynamic models have been used to estimate joint kinetics during various activities. Kinetics estimation is in demand in sports and clinical applications where data on external forces, such as the ground reaction force (GRF), are not available. The purpose of this study was to estimate the GRF during gait by utilizing distance- and velocity-dependent force models between the foot and ground in an inverse-dynamics-based optimization. Ten males were tested as they walked at four different speeds on a force plate-embedded treadmill system. The full-GRF model whose foot-ground reaction elements were dynamically adjusted according to vertical displacement and anterior-posterior speed between the foot and ground was implemented in a full-body skeletal model. The model estimated the vertical and shear forces of the GRF from body kinematics. The shear-GRF model with dynamically adjustable shear reaction elements according to the input vertical force was also implemented in the foot of a full-body skeletal model. Shear forces of the GRF were estimated from body kinematics, vertical GRF, and center of pressure. The estimated full GRF had the lowest root mean square (RMS) errors at the slow walking speed (1.0m/s) with 4.2, 1.3, and 5.7% BW for anterior-posterior, medial-lateral, and vertical forces, respectively. The estimated shear forces were not significantly different between the full-GRF and shear-GRF models, but the RMS errors of the estimated knee joint kinetics were significantly lower for the shear-GRF model. Providing COP and vertical GRF with sensors, such as an insole-type pressure mat, can help estimate shear forces of the GRF and increase accuracy for estimation of joint kinetics. Copyright © 2016 Elsevier B.V. All rights reserved.

[Effect of social desirability on dietary intake estimated from a food questionnaire].

PubMed

Barros, Renata; Moreira, Pedro; Oliveira, Bruno

2005-01-01

Self-report of dietary intake could be biased by social thus affecting risk estimates in epidemiological studies. The objective of study was to assess the effect of social desirability on dietary intake from a food frequency questionnaire (FFQ). A convenience sample of 483 Portuguese university students was recruited. Subjects were invited to complete a two-part self-administered questionnaire: the first part included the Marlowe-Crowne Social Desirability Scale (M-CSDS), a physical activity questionnaire and self-reported height and weight; the second part, included a semi-quantitative FFQ validated for Portuguese adults, that should be returned after fulfillment. All subjects completed the first part of the questionnaire and 40.4% returned the FFQ fairly completed. In multiple regression analysis, after adjustment for energy and confounders, social desirability produced a significant positive effect in the estimates of dietary fibre, vitamin C, vitamin E, magnesium and potassium, in both genders. In multiple regression, after adjustment for energy and confounders, social desirability had a significant positive effect in the estimates of vegetable consumption, for both genders, and a negative effect in white bread and beer, for women. Social desirability affected nutritional and food intake estimated from a food frequency questionnaire.

Evaluation and adjustment of altimeter measurement and numerical hindcast in wave height trend estimation in China's coastal seas

NASA Astrophysics Data System (ADS)

Li, Shuiqing; Guan, Shoude; Hou, Yijun; Liu, Yahao; Bi, Fan

2018-05-01

A long-term trend of significant wave height (SWH) in China's coastal seas was examined based on three datasets derived from satellite measurements and numerical hindcasts. One set of altimeter data were obtained from the GlobWave, while the other two datasets of numerical hindcasts were obtained from the third-generation wind wave model, WAVEWATCH III, forced by wind fields from the Cross-Calibrated Multi-Platform (CCMP) and NCEP's Climate Forecast System Reanalysis (CFSR). The mean and extreme wave trends were estimated for the period 1992-2010 with respect to the annual mean and the 99th-percentile values of SWH, respectively. The altimeter wave trend estimates feature considerable uncertainties owing to the sparse sampling rate. Furthermore, the extreme wave trend tends to be overestimated because of the increasing sampling rate over time. Numerical wave trends strongly depend on the quality of the wind fields, as the CCMP waves significantly overestimate the wave trend, whereas the CFSR waves tend to underestimate the trend. Corresponding adjustments were applied which effectively improved the trend estimates from the altimeter and numerical data. The adjusted results show generally increasing mean wave trends, while the extreme wave trends are more spatially-varied, from decreasing trends prevailing in the South China Sea to significant increasing trends mainly in the East China Sea.

An evaluation of bias in propensity score-adjusted non-linear regression models.

PubMed

Wan, Fei; Mitra, Nandita

2018-03-01

Propensity score methods are commonly used to adjust for observed confounding when estimating the conditional treatment effect in observational studies. One popular method, covariate adjustment of the propensity score in a regression model, has been empirically shown to be biased in non-linear models. However, no compelling underlying theoretical reason has been presented. We propose a new framework to investigate bias and consistency of propensity score-adjusted treatment effects in non-linear models that uses a simple geometric approach to forge a link between the consistency of the propensity score estimator and the collapsibility of non-linear models. Under this framework, we demonstrate that adjustment of the propensity score in an outcome model results in the decomposition of observed covariates into the propensity score and a remainder term. Omission of this remainder term from a non-collapsible regression model leads to biased estimates of the conditional odds ratio and conditional hazard ratio, but not for the conditional rate ratio. We further show, via simulation studies, that the bias in these propensity score-adjusted estimators increases with larger treatment effect size, larger covariate effects, and increasing dissimilarity between the coefficients of the covariates in the treatment model versus the outcome model.

Using sightability-adjusted brood-pair ratios to estimate waterfowl productivity

USGS Publications Warehouse

Pagano, Anthony M.; Amundson, Courtney L.; Pieron, Matthew R.; Arnold, Todd W.; Kimmel, Timothy C.

2014-01-01

Historically, biologists used brood-pair ratios (BPRs) as an index to waterfowl productivity to help guide management decisions and evaluate conservation practices. However, BPRs are biased by imperfect detection probabilities, especially for broods. We conducted roadside surveys for breeding waterfowl pairs on 7–8 study sites in the springs of 2006–2008 in northeastern North Dakota, USA. Later each year, we conducted replicate counts of broods on the same wetlands and used mark–recapture methods to estimate sightability-adjusted BPRs (SA-BPRs). Traditional roadside brood surveys detected only 30–45% of the available broods, depending on species. We explored the potential for using SA-BPRs to measure hen success (i.e., the probability a female hatches ≥1 egg across all nesting attempts) for mallards (Anas platyrhynchos) and other upland-nesting dabbling ducks (Anas spp.). We found that SA-BPRs explained 40% of the variation in hen success over 5 species of dabbling ducks, and we were able to detect an effect of predator reduction on hen success in combined dabblers, but not in mallards alone. However, we found no relationship between SA-BPRs and mallard fledging rates (hen success × initial brood size × duckling survival). Our results suggest that SA-BPRs can provide a cost-effective alternative to traditional measures of productivity such as nesting success, but not to measures of duckling survival. Nevertheless, SA-BPRs may be useful in areas where traditional measures of waterfowl productivity are logistically or financially challenging.

On the Performance of Maximum Likelihood versus Means and Variance Adjusted Weighted Least Squares Estimation in CFA

ERIC Educational Resources Information Center

Beauducel, Andre; Herzberg, Philipp Yorck

2006-01-01

This simulation study compared maximum likelihood (ML) estimation with weighted least squares means and variance adjusted (WLSMV) estimation. The study was based on confirmatory factor analyses with 1, 2, 4, and 8 factors, based on 250, 500, 750, and 1,000 cases, and on 5, 10, 20, and 40 variables with 2, 3, 4, 5, and 6 categories. There was no…

Q-adjusting technique applied to vertical deflections estimation in a single-axis rotation INS/GPS integrated system

NASA Astrophysics Data System (ADS)

Zhu, Jing; Wang, Xingshu; Wang, Jun; Dai, Dongkai; Xiong, Hao

2016-10-01

Former studies have proved that the attitude error in a single-axis rotation INS/GPS integrated system tracks the high frequency component of the deflections of the vertical (DOV) with a fixed delay and tracking error. This paper analyses the influence of the nominal process noise covariance matrix Q on the tracking error as well as the response delay, and proposed a Q-adjusting technique to obtain the attitude error which can track the DOV better. Simulation results show that different settings of Q lead to different response delay and tracking error; there exists optimal Q which leads to a minimum tracking error and a comparatively short response delay; for systems with different accuracy, different Q-adjusting strategy should be adopted. In this way, the DOV estimation accuracy of using the attitude error as the observation can be improved. According to the simulation results, the DOV estimation accuracy after using the Q-adjusting technique is improved by approximate 23% and 33% respectively compared to that of the Earth Model EGM2008 and the direct attitude difference method.

Viscosity-adjusted estimation of pressure head and pump flow with quasi-pulsatile modulation of rotary blood pump for a total artificial heart.

PubMed

Yurimoto, Terumi; Hara, Shintaro; Isoyama, Takashi; Saito, Itsuro; Ono, Toshiya; Abe, Yusuke

2016-09-01

Estimation of pressure and flow has been an important subject for developing implantable artificial hearts. To realize real-time viscosity-adjusted estimation of pressure head and pump flow for a total artificial heart, we propose the table estimation method with quasi-pulsatile modulation of rotary blood pump in which systolic high flow and diastolic low flow phased are generated. The table estimation method utilizes three kinds of tables: viscosity, pressure and flow tables. Viscosity is estimated from the characteristic that differential value in motor speed between systolic and diastolic phases varies depending on viscosity. Potential of this estimation method was investigated using mock circulation system. Glycerin solution diluted with salty water was used to adjust viscosity of fluid. In verification of this method using continuous flow data, fairly good estimation could be possible when differential pulse width modulation (PWM) value of the motor between systolic and diastolic phases was high. In estimation under quasi-pulsatile condition, inertia correction was provided and fairly good estimation was possible when the differential PWM value was high, which was not different from the verification results using continuous flow data. In the experiment of real-time estimation applying moving average method to the estimated viscosity, fair estimation could be possible when the differential PWM value was high, showing that real-time viscosity-adjusted estimation of pressure head and pump flow would be possible with this novel estimation method when the differential PWM value would be set high.

Effect of urine urea nitrogen and protein intake adjusted by using the estimated urine creatinine excretion rate on the antiproteinuric effect of angiotensin II type I receptor blockers.

PubMed

Chin, Ho Jun; Kim, Dong Ki; Park, Jung Hwan; Shin, Sung Joon; Lee, Sang Ho; Choi, Bum Soon; Kim, Suhnggwon; Lim, Chun Soo

2015-01-01

The aim of this study was to determine the role of protein intake on proteinuria in chronic kidney disease (CKD), as it is presently not conclusive. This is a subanalysis of data from an open-label, case-controlled, randomized clinical trial on education about low-salt diets (NCT01552954). We estimated the urine excretion rate of parameters in a day, adjusted by using the equation for estimating urine creatinine excretion, and analyzed the effect of urine urea nitrogen (UUN), as well as estimating protein intake on the level of albuminuria in hypertensive patients with chronic kidney disease. Among 174 participants from whom complete 24-h urine specimens were collected, the estimates from the Tanaka equation resulted in the highest accuracy for the urinary excretion rate of creatinine, sodium, albumin, and UUN. Among 227 participants, the baseline value of estimated urine albumin excretion (eUalb) was positively correlated with the estimated UUN (eUUN) or protein intake according to eUUN (P = 0.012 and P = 0.038, respectively). We were able to calculate the ratios of eUalb and eUUN in 221 participants and grouped them according to the ratio of eUUN during 16-wk trial period. The proportion of patients that achieved a decrement of eUalb ≥25% during 16 wk with an angiotensin II type I receptor blocker (ARB) medication was 80% (24 of 30) in group 1, with eUUN ratio ≤-25%; 82.2% (111 of 135) in group 2, with eUUN ratio between -25% and 25%; and 66.1% (37 and 56) in group 3, with eUUN ratio ≥25% (P = 0.048). The probability of a decrease in albuminuria with ARB treatment was lower in patients with an increase of eUUN or protein intake during the 16 wk of ARB treatment, as observed in multiple logistic regression analysis as well. The estimated urine urea excretion rate showed a positive association with the level of albuminuria in hypertensive patients with chronic kidney disease. The increase of eUUN excretion ameliorated the antiproteinuric effect of ARB

Global Burden of Leptospirosis: Estimated in Terms of Disability Adjusted Life Years

PubMed Central

Torgerson, Paul R.; Hagan, José E.; Costa, Federico; Calcagno, Juan; Kane, Michael; Martinez-Silveira, Martha S.; Goris, Marga G. A.; Stein, Claudia; Ko, Albert I.; Abela-Ridder, Bernadette

2015-01-01

Background Leptospirosis, a spirochaetal zoonosis, occurs in diverse epidemiological settings and affects vulnerable populations, such as rural subsistence farmers and urban slum dwellers. Although leptospirosis can cause life-threatening disease, there is no global burden of disease estimate in terms of Disability Adjusted Life Years (DALYs) available. Methodology/Principal Findings We utilised the results of a parallel publication that reported global estimates of morbidity and mortality due to leptospirosis. We estimated Years of Life Lost (YLLs) from age and gender stratified mortality rates. Years of Life with Disability (YLDs) were developed from a simple disease model indicating likely sequelae. DALYs were estimated from the sum of YLLs and YLDs. The study suggested that globally approximately 2·90 million DALYs are lost per annum (UIs 1·25–4·54 million) from the approximately annual 1·03 million cases reported previously. Males are predominantly affected with an estimated 2·33 million DALYs (UIs 0·98–3·69) or approximately 80% of the total burden. For comparison, this is over 70% of the global burden of cholera estimated by GBD 2010. Tropical regions of South and South-east Asia, Western Pacific, Central and South America, and Africa had the highest estimated leptospirosis disease burden. Conclusions/Significance Leptospirosis imparts a significant health burden worldwide, which approach or exceed those encountered for a number of other zoonotic and neglected tropical diseases. The study findings indicate that highest burden estimates occur in resource-poor tropical countries, which include regions of Africa where the burden of leptospirosis has been under-appreciated and possibly misallocated to other febrile illnesses such as malaria. PMID:26431366

Adolescent leisure dimensions, psychosocial adjustment, and gender effects.

PubMed

Bradley, Graham L; Inglis, Brad C

2012-10-01

Leisure provides the context for much of adolescent behaviour and development. While both theory and research point to the benefits of participation in leisure activities that are highly structured, the association between structured leisure and psychosocial adjustment is not uniformly high. This paper presents a model of adolescent leisure comprising three dimensions: structure, effort, and social contact. Adolescent adjustment is hypothesized to increase with participation in activities characterized by each of these attributes. Adjustment is also predicted to vary with gender, and with the interaction of gender and leisure participation. These propositions were tested in a questionnaire-based study of 433 Australian adolescents. Results revealed majority support for hypotheses pertaining to the positive effects of the leisure dimensions, and for gender differences in leisure participation and adjustment. Evidence was also obtained of gender-differentiated effects of leisure on adjustment, with social leisure predicting adjustment more strongly in females than males. Copyright © 2012 The Foundation for Professionals in Services for Adolescents. Published by Elsevier Ltd. All rights reserved.

Estimating the occupancy of spotted owl habitat areas by sampling and adjusting for bias

Treesearch

David L. Azuma; James A. Baldwin; Barry R. Noon

1990-01-01

A basic sampling scheme is proposed to estimate the proportion of sampled units (Spotted Owl Habitat Areas (SOHAs) or randomly sampled 1000-acre polygon areas (RSAs)) occupied by spotted owl pairs. A bias adjustment for the possibility of missing a pair given its presence on a SOHA or RSA is suggested. The sampling scheme is based on a fixed number of visits to a...

Estimating Teacher Effectiveness from Two-Year Changes in Students' Test Scores

ERIC Educational Resources Information Center

Leigh, Andrew

2010-01-01

Using a dataset covering over 10,000 Australian school teachers and over 90,000 pupils, I estimate how effective teachers are in raising students' test scores. Since the exams are biennial, it is necessary to take account of the teacher's work in the intervening year. Even adjusting for measurement error, the teacher fixed effects are widely…

Covariate Imbalance and Adjustment for Logistic Regression Analysis of Clinical Trial Data

PubMed Central

Ciolino, Jody D.; Martin, Reneé H.; Zhao, Wenle; Jauch, Edward C.; Hill, Michael D.; Palesch, Yuko Y.

2014-01-01

In logistic regression analysis for binary clinical trial data, adjusted treatment effect estimates are often not equivalent to unadjusted estimates in the presence of influential covariates. This paper uses simulation to quantify the benefit of covariate adjustment in logistic regression. However, International Conference on Harmonization guidelines suggest that covariate adjustment be pre-specified. Unplanned adjusted analyses should be considered secondary. Results suggest that that if adjustment is not possible or unplanned in a logistic setting, balance in continuous covariates can alleviate some (but never all) of the shortcomings of unadjusted analyses. The case of log binomial regression is also explored. PMID:24138438

Adjustment for reporting bias in network meta-analysis of antidepressant trials

PubMed Central

2012-01-01

Background Network meta-analysis (NMA), a generalization of conventional MA, allows for assessing the relative effectiveness of multiple interventions. Reporting bias is a major threat to the validity of MA and NMA. Numerous methods are available to assess the robustness of MA results to reporting bias. We aimed to extend such methods to NMA. Methods We introduced 2 adjustment models for Bayesian NMA. First, we extended a meta-regression model that allows the effect size to depend on its standard error. Second, we used a selection model that estimates the propensity of trial results being published and in which trials with lower propensity are weighted up in the NMA model. Both models rely on the assumption that biases are exchangeable across the network. We applied the models to 2 networks of placebo-controlled trials of 12 antidepressants, with 74 trials in the US Food and Drug Administration (FDA) database but only 51 with published results. NMA and adjustment models were used to estimate the effects of the 12 drugs relative to placebo, the 66 effect sizes for all possible pair-wise comparisons between drugs, probabilities of being the best drug and ranking of drugs. We compared the results from the 2 adjustment models applied to published data and NMAs of published data and NMAs of FDA data, considered as representing the totality of the data. Results Both adjustment models showed reduced estimated effects for the 12 drugs relative to the placebo as compared with NMA of published data. Pair-wise effect sizes between drugs, probabilities of being the best drug and ranking of drugs were modified. Estimated drug effects relative to the placebo from both adjustment models were corrected (i.e., similar to those from NMA of FDA data) for some drugs but not others, which resulted in differences in pair-wise effect sizes between drugs and ranking. Conclusions In this case study, adjustment models showed that NMA of published data was not robust to reporting bias and

Effects of parent drug use and personality on toddler adjustment.

PubMed

Brook, J S; Whiteman, M; Shapiro, J; Cohen, P

1996-03-01

The interrelation between parental drug use and parental personality and the effects on 18-month-old children's adjustment were examined. Data on the parents were available at four points in time: Time 1 at mean age 6.1 years, Time 2 at mean age 13.7 years, Time 3 at mean age 16.4 years, and at Time 4 at mean age 22.2 years. Data on their toddlers at 18 months of age were also available. Structured interviews were used to assess personality and drug use and the toddlers' adjustment. Time 3 parental personality traits were related to Time 4 personality traits, which in turn were related to toddler adjustment. The influence of parental alcohol involvement (Time 3) on toddler adjustment was mediated by parental personality (Times 3 and 4) and parental alcohol problems (Time 4). Interactive effects demonstrated that protective parental personality traits (nondrug conducive) enhanced the effects of low parental drug use, resulting in the highest amounts of toddler adjustment. There are significant pathways between parental personality and drug use and toddler adjustment. Parental protective factors enhance the effect of parental low drug use on toddler adjustment.

Adjusting survival time estimates to account for treatment switching in randomized controlled trials--an economic evaluation context: methods, limitations, and recommendations.

PubMed

Latimer, Nicholas R; Abrams, Keith R; Lambert, Paul C; Crowther, Michael J; Wailoo, Allan J; Morden, James P; Akehurst, Ron L; Campbell, Michael J

2014-04-01

Treatment switching commonly occurs in clinical trials of novel interventions in the advanced or metastatic cancer setting. However, methods to adjust for switching have been used inconsistently and potentially inappropriately in health technology assessments (HTAs). We present recommendations on the use of methods to adjust survival estimates in the presence of treatment switching in the context of economic evaluations. We provide background on the treatment switching issue and summarize methods used to adjust for it in HTAs. We discuss the assumptions and limitations associated with adjustment methods and draw on results of a simulation study to make recommendations on their use. We demonstrate that methods used to adjust for treatment switching have important limitations and often produce bias in realistic scenarios. We present an analysis framework that aims to increase the probability that suitable adjustment methods can be identified on a case-by-case basis. We recommend that the characteristics of clinical trials, and the treatment switching mechanism observed within them, should be considered alongside the key assumptions of the adjustment methods. Key assumptions include the "no unmeasured confounders" assumption associated with the inverse probability of censoring weights (IPCW) method and the "common treatment effect" assumption associated with the rank preserving structural failure time model (RPSFTM). The limitations associated with switching adjustment methods such as the RPSFTM and IPCW mean that they are appropriate in different scenarios. In some scenarios, both methods may be prone to bias; "2-stage" methods should be considered, and intention-to-treat analyses may sometimes produce the least bias. The data requirements of adjustment methods also have important implications for clinical trialists.

Aerial surveys adjusted by ground surveys to estimate area occupied by black-tailed prairie dog colonies

USGS Publications Warehouse

Sidle, John G.; Augustine, David J.; Johnson, Douglas H.; Miller, Sterling D.; Cully, Jack F.; Reading, Richard P.

2012-01-01

Aerial surveys using line-intercept methods are one approach to estimate the extent of prairie dog colonies in a large geographic area. Although black-tailed prairie dogs (Cynomys ludovicianus) construct conspicuous mounds at burrow openings, aerial observers have difficulty discriminating between areas with burrows occupied by prairie dogs (colonies) versus areas of uninhabited burrows (uninhabited colony sites). Consequently, aerial line-intercept surveys may overestimate prairie dog colony extent unless adjusted by an on-the-ground inspection of a sample of intercepts. We compared aerial line-intercept surveys conducted over 2 National Grasslands in Colorado, USA, with independent ground-mapping of known black-tailed prairie dog colonies. Aerial line-intercepts adjusted by ground surveys using a single activity category adjustment overestimated colonies by ≥94% on the Comanche National Grassland and ≥58% on the Pawnee National Grassland. We present a ground-survey technique that involves 1) visiting on the ground a subset of aerial intercepts classified as occupied colonies plus a subset of intercepts classified as uninhabited colony sites, and 2) based on these ground observations, recording the proportion of each aerial intercept that intersects a colony and the proportion that intersects an uninhabited colony site. Where line-intercept techniques are applied to aerial surveys or remotely sensed imagery, this method can provide more accurate estimates of black-tailed prairie dog abundance and trends

Do Adjusting-Amount and Adjusting-Delay Procedures Produce Equivalent Estimates of Subjective Value in Pigeons?

ERIC Educational Resources Information Center

Green, Leonard; Myerson, Joel; Shah, Anuj K.; Estle, Sara J.; Holt, Daniel D.

2007-01-01

The current experiment examined whether adjusting-amount and adjusting-delay procedures provide equivalent measures of discounting. Pigeons' discounting on the two procedures was compared using a within-subject yoking technique in which the indifference point (number of pellets or time until reinforcement) obtained with one procedure determined…

Estimating contaminant loads in rivers: An application of adjusted maximum likelihood to type 1 censored data

USGS Publications Warehouse

Cohn, Timothy A.

2005-01-01

This paper presents an adjusted maximum likelihood estimator (AMLE) that can be used to estimate fluvial transport of contaminants, like phosphorus, that are subject to censoring because of analytical detection limits. The AMLE is a generalization of the widely accepted minimum variance unbiased estimator (MVUE), and Monte Carlo experiments confirm that it shares essentially all of the MVUE's desirable properties, including high efficiency and negligible bias. In particular, the AMLE exhibits substantially less bias than alternative censored‐data estimators such as the MLE (Tobit) or the MLE followed by a jackknife. As with the MLE and the MVUE the AMLE comes close to achieving the theoretical Frechet‐Cramér‐Rao bounds on its variance. This paper also presents a statistical framework, applicable to both censored and complete data, for understanding and estimating the components of uncertainty associated with load estimates. This can serve to lower the cost and improve the efficiency of both traditional and real‐time water quality monitoring.

Adjusting HIV prevalence estimates for non-participation: an application to demographic surveillance

PubMed Central

McGovern, Mark E.; Marra, Giampiero; Radice, Rosalba; Canning, David; Newell, Marie-Louise; Bärnighausen, Till

2015-01-01

Introduction HIV testing is a cornerstone of efforts to combat the HIV epidemic, and testing conducted as part of surveillance provides invaluable data on the spread of infection and the effectiveness of campaigns to reduce the transmission of HIV. However, participation in HIV testing can be low, and if respondents systematically select not to be tested because they know or suspect they are HIV positive (and fear disclosure), standard approaches to deal with missing data will fail to remove selection bias. We implemented Heckman-type selection models, which can be used to adjust for missing data that are not missing at random, and established the extent of selection bias in a population-based HIV survey in an HIV hyperendemic community in rural South Africa. Methods We used data from a population-based HIV survey carried out in 2009 in rural KwaZulu-Natal, South Africa. In this survey, 5565 women (35%) and 2567 men (27%) provided blood for an HIV test. We accounted for missing data using interviewer identity as a selection variable which predicted consent to HIV testing but was unlikely to be independently associated with HIV status. Our approach involved using this selection variable to examine the HIV status of residents who would ordinarily refuse to test, except that they were allocated a persuasive interviewer. Our copula model allows for flexibility when modelling the dependence structure between HIV survey participation and HIV status. Results For women, our selection model generated an HIV prevalence estimate of 33% (95% CI 27–40) for all people eligible to consent to HIV testing in the survey. This estimate is higher than the estimate of 24% generated when only information from respondents who participated in testing is used in the analysis, and the estimate of 27% when imputation analysis is used to predict missing data on HIV status. For men, we found an HIV prevalence of 25% (95% CI 15–35) using the selection model, compared to 16% among those who

Confounding adjustment in comparative effectiveness research conducted within distributed research networks.

PubMed

Toh, Sengwee; Gagne, Joshua J; Rassen, Jeremy A; Fireman, Bruce H; Kulldorff, Martin; Brown, Jeffrey S

2013-08-01

A distributed research network (DRN) of electronic health care databases, in which data reside behind the firewall of each data partner, can support a wide range of comparative effectiveness research (CER) activities. An essential component of a fully functional DRN is the capability to perform robust statistical analyses to produce valid, actionable evidence without compromising patient privacy, data security, or proprietary interests. We describe the strengths and limitations of different confounding adjustment approaches that can be considered in observational CER studies conducted within DRNs, and the theoretical and practical issues to consider when selecting among them in various study settings. Several methods can be used to adjust for multiple confounders simultaneously, either as individual covariates or as confounder summary scores (eg, propensity scores and disease risk scores), including: (1) centralized analysis of patient-level data, (2) case-centered logistic regression of risk set data, (3) stratified or matched analysis of aggregated data, (4) distributed regression analysis, and (5) meta-analysis of site-specific effect estimates. These methods require different granularities of information be shared across sites and afford investigators different levels of analytic flexibility. DRNs are growing in use and sharing of highly detailed patient-level information is not always feasible in DRNs. Methods that incorporate confounder summary scores allow investigators to adjust for a large number of confounding factors without the need to transfer potentially identifiable information in DRNs. They have the potential to let investigators perform many analyses traditionally conducted through a centralized dataset with detailed patient-level information.

Effects of early exposure and lifetime exposure to intimate partner violence (IPV) on child adjustment.

PubMed

Graham-Bermann, Sandra A; Perkins, Suzanne

2010-01-01

Children exposed to overwhelming and potentially traumatic events early in their lives are considered at-risk for problems in adjustment. Yet it is not known whether it is the age of first exposure (AFE) to violence or the amount of violence that the child witnessed in their lifetime that has the greatest impact on adjustment. For a sample of 190 children ages 6 to 12 exposed to intimate partner violence, their mothers reported that the average length of their abusive relationship was 10 years. The majority of children were first exposed to family violence as infants (64%), with only 12% first exposed when school-aged. Both the AFE and an estimate of the cumulative amount of violence were significantly and negatively related to children's behavioral problems. However, in regression analyses controlling for child sex, ethnicity, age, and family environment variables, cumulative violence exposure accounted for greater variance in adjustment than did AFE. Furthermore, cumulative violence exposure mediated the relationship between AFE and externalizing behavior problems, indicating that the cumulative exposure to IPV outweighed the AFE in its effect on child adjustment.

Impact of work-related cancers in Taiwan-Estimation with QALY (quality-adjusted life year) and healthcare costs.

PubMed

Lee, Lukas Jyuhn-Hsiarn; Lin, Cheng-Kuan; Hung, Mei-Chuan; Wang, Jung-Der

2016-12-01

This study estimates the annual numbers of eight work-related cancers, total losses of quality-adjusted life years (QALYs), and lifetime healthcare expenditures that possibly could be saved by improving occupational health in Taiwan. Three databases were interlinked: the Taiwan Cancer Registry, the National Mortality Registry, and the National Health Insurance Research Database. Annual numbers of work-related cancers were estimated based on attributable fractions (AFs) abstracted from a literature review. The survival functions for eight cancers were estimated and extrapolated to lifetime using a semi-parametric method. A convenience sample of 8846 measurements of patients' quality of life with EQ-5D was collected for utility values and multiplied by survival functions to estimate quality-adjusted life expectancies (QALEs). The loss-of-QALE was obtained by subtracting the QALE of cancer from age- and sex-matched referents simulated from national vital statistics. The lifetime healthcare expenditures were estimated by multiplying the survival probability with mean monthly costs paid by the National Health Insurance for cancer diagnosis and treatment and summing this for the expected lifetime. A total of 3010 males and 726 females with eight work-related cancers were estimated in 2010. Among them, lung cancer ranked first in terms of QALY loss, with an annual total loss-of-QALE of 28,463 QALYs and total lifetime healthcare expenditures of US$36.6 million. Successful prevention of eight work-related cancers would not only avoid the occurrence of 3736 cases of cancer, but would also save more than US$70 million in healthcare costs and 46,750 QALYs for the Taiwan society in 2010.

Sample size re-estimation and other midcourse adjustments with sequential parallel comparison design.

PubMed

Silverman, Rachel K; Ivanova, Anastasia

2017-01-01

Sequential parallel comparison design (SPCD) was proposed to reduce placebo response in a randomized trial with placebo comparator. Subjects are randomized between placebo and drug in stage 1 of the trial, and then, placebo non-responders are re-randomized in stage 2. Efficacy analysis includes all data from stage 1 and all placebo non-responding subjects from stage 2. This article investigates the possibility to re-estimate the sample size and adjust the design parameters, allocation proportion to placebo in stage 1 of SPCD, and weight of stage 1 data in the overall efficacy test statistic during an interim analysis.

Estimating the effect of a rare time-dependent treatment on the recurrent event rate.

PubMed

Smith, Abigail R; Zhu, Danting; Goodrich, Nathan P; Merion, Robert M; Schaubel, Douglas E

2018-05-30

In many observational studies, the objective is to estimate the effect of treatment or state-change on the recurrent event rate. If treatment is assigned after the start of follow-up, traditional methods (eg, adjustment for baseline-only covariates or fully conditional adjustment for time-dependent covariates) may give biased results. We propose a two-stage modeling approach using the method of sequential stratification to accurately estimate the effect of a time-dependent treatment on the recurrent event rate. At the first stage, we estimate the pretreatment recurrent event trajectory using a proportional rates model censored at the time of treatment. Prognostic scores are estimated from the linear predictor of this model and used to match treated patients to as yet untreated controls based on prognostic score at the time of treatment for the index patient. The final model is stratified on matched sets and compares the posttreatment recurrent event rate to the recurrent event rate of the matched controls. We demonstrate through simulation that bias due to dependent censoring is negligible, provided the treatment frequency is low, and we investigate a threshold at which correction for dependent censoring is needed. The method is applied to liver transplant (LT), where we estimate the effect of development of post-LT End Stage Renal Disease (ESRD) on rate of days hospitalized. Copyright © 2018 John Wiley & Sons, Ltd.

A new methodological approach to adjust alcohol exposure distributions to improve the estimation of alcohol-attributable fractions.

PubMed

Parish, William J; Aldridge, Arnie; Allaire, Benjamin; Ekwueme, Donatus U; Poehler, Diana; Guy, Gery P; Thomas, Cheryll C; Trogdon, Justin G

2017-11-01

To assess the burden of excessive alcohol use, researchers estimate alcohol-attributable fractions (AAFs) routinely. However, under-reporting in survey data can bias these estimates. We present an approach that adjusts for under-reporting in the estimation of AAFs, particularly within subgroups. This framework is a refinement of a previous method conducted by Rehm et al. We use a measurement error model to derive the 'true' alcohol distribution from a 'reported' alcohol distribution. The 'true' distribution leverages per-capita sales data to identify the distribution average and then identifies the shape of the distribution with self-reported survey data. Data are from the National Alcohol Survey (NAS), the National Household Survey on Drug Abuse (NHSDA) and the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC). We compared our approach with previous approaches by estimating the AAF of female breast cancer cases. Compared with Rehm et al.'s approach, our refinement performs similarly under a gamma assumption. For example, among females aged 18-25 years, the two approaches produce estimates from NHSDA that are within a percentage point. However, relaxing the gamma assumption generally produces more conservative evidence. For example, among females aged 18-25 years, estimates from NHSDA based on the best-fitting distribution are only 19.33% of breast cancer cases, which is a much smaller proportion than the gamma-based estimates of approximately 28%. A refinement of Rehm et al.'s approach to adjusting for underreporting in the estimation of alcohol-attributable fractions provides more flexibility. This flexibility can avoid biases associated with failing to account for the underlying differences in alcohol consumption patterns across different study populations. Comparisons of our refinement with Rehm et al.'s approach show that results are similar when a gamma distribution is assumed. However, results are appreciably lower when the best

Nonparametric methods for doubly robust estimation of continuous treatment effects.

PubMed

Kennedy, Edward H; Ma, Zongming; McHugh, Matthew D; Small, Dylan S

2017-09-01

Continuous treatments (e.g., doses) arise often in practice, but many available causal effect estimators are limited by either requiring parametric models for the effect curve, or by not allowing doubly robust covariate adjustment. We develop a novel kernel smoothing approach that requires only mild smoothness assumptions on the effect curve, and still allows for misspecification of either the treatment density or outcome regression. We derive asymptotic properties and give a procedure for data-driven bandwidth selection. The methods are illustrated via simulation and in a study of the effect of nurse staffing on hospital readmissions penalties.

Cause-specific premature death from ambient PM2.5 exposure in India: Estimate adjusted for baseline mortality.

PubMed

Chowdhury, Sourangsu; Dey, Sagnik

2016-05-01

In India, more than a billion population is at risk of exposure to ambient fine particulate matter (PM2.5) concentration exceeding World Health Organization air quality guideline, posing a serious threat to health. Cause-specific premature death from ambient PM2.5 exposure is poorly known for India. Here we develop a non-linear power law (NLP) function to estimate the relative risk associated with ambient PM2.5 exposure using satellite-based PM2.5 concentration (2001-2010) that is bias-corrected against coincident direct measurements. We show that estimate of annual premature death in India is lower by 14.7% (19.2%) using NLP (integrated exposure risk function, IER) for assumption of uniform baseline mortality across India (as considered in the global burden of disease study) relative to the estimate obtained by adjusting for state-specific baseline mortality using GDP as a proxy. 486,100 (811,000) annual premature death in India is estimated using NLP (IER) risk functions after baseline mortality adjustment. 54.5% of premature death estimated using NLP risk function is attributed to chronic obstructive pulmonary disease (COPD), 24.0% to ischemic heart disease (IHD), 18.5% to stroke and the remaining 3.0% to lung cancer (LC). 44,900 (5900-173,300) less premature death is expected annually, if India achieves its present annual air quality target of 40μgm(-3). Our results identify the worst affected districts in terms of ambient PM2.5 exposure and resulting annual premature death and call for initiation of long-term measures through a systematic framework of pollution and health data archive. Copyright © 2016 Elsevier Ltd. All rights reserved.

[Evaluation of the adjusted amino acid score by digestibility for estimating the protein quality and protein available in food and diets].

PubMed

Pak, N; Vera, G; Araya, H

1985-03-01

The purpose of the present study was to evaluate the amino acid score adjusted by digestibility to estimate protein quality and utilizable protein in foods and diets, considering net protein utilization (NPU) as a biological reference method. Ten foods of vegetable origin and ten of animal origin, as well as eight mixtures of foods of vegetable and animal origin were studied. When all the foods were considered, a positive (r = 0.83) and highly significant correlation (p less than 0.001) between NPU and the amino acid score adjusted by digestibility was found. When the foods were separated according to their origin, this correlation was positive only for the foods of vegetable origin (r = 0.93) and statistically significant (p less than 0.001). Also, only in those foods were similar values found between NPU and amino acid score adjusted by digestibility, as well as in utilizable protein estimated considering both methods. Caution is required to interpret protein quality and utilizable protein values of foods of animal origin and mixtures of foods of vegetable and animal origin when the amino acid score method adjusted by digestibility, or NPU, are utilized.

A clinical economics workstation for risk-adjusted health care cost management.

PubMed Central

Eisenstein, E. L.; Hales, J. W.

1995-01-01

This paper describes a healthcare cost accounting system which is under development at Duke University Medical Center. Our approach differs from current practice in that this system will dynamically adjust its resource usage estimates to compensate for variations in patient risk levels. This adjustment is made possible by introducing a new cost accounting concept, Risk-Adjusted Quantity (RQ). RQ divides case-level resource usage variances into their risk-based component (resource consumption differences attributable to differences in patient risk levels) and their non-risk-based component (resource consumption differences which cannot be attributed to differences in patient risk levels). Because patient risk level is a factor in estimating resource usage, this system is able to simultaneously address the financial and quality dimensions of case cost management. In effect, cost-effectiveness analysis is incorporated into health care cost management. PMID:8563361

Empirical estimation of present-day Antarctic glacial isostatic adjustment and ice mass change

NASA Astrophysics Data System (ADS)

Gunter, B. C.; Didova, O.; Riva, R. E. M.; Ligtenberg, S. R. M.; Lenaerts, J. T. M.; King, M. A.; van den Broeke, M. R.; Urban, T.

2014-04-01

This study explores an approach that simultaneously estimates Antarctic mass balance and glacial isostatic adjustment (GIA) through the combination of satellite gravity and altimetry data sets. The results improve upon previous efforts by incorporating a firn densification model to account for firn compaction and surface processes as well as reprocessed data sets over a slightly longer period of time. A range of different Gravity Recovery and Climate Experiment (GRACE) gravity models were evaluated and a new Ice, Cloud, and Land Elevation Satellite (ICESat) surface height trend map computed using an overlapping footprint approach. When the GIA models created from the combination approach were compared to in situ GPS ground station displacements, the vertical rates estimated showed consistently better agreement than recent conventional GIA models. The new empirically derived GIA rates suggest the presence of strong uplift in the Amundsen Sea sector in West Antarctica (WA) and the Philippi/Denman sectors, as well as subsidence in large parts of East Antarctica (EA). The total GIA-related mass change estimates for the entire Antarctic ice sheet ranged from 53 to 103 Gt yr-1, depending on the GRACE solution used, with an estimated uncertainty of ±40 Gt yr-1. Over the time frame February 2003-October 2009, the corresponding ice mass change showed an average value of -100 ± 44 Gt yr-1 (EA: 5 ± 38, WA: -105 ± 22), consistent with other recent estimates in the literature, with regional mass loss mostly concentrated in WA. The refined approach presented in this study shows the contribution that such data combinations can make towards improving estimates of present-day GIA and ice mass change, particularly with respect to determining more reliable uncertainties.

Baseline adjustments for binary data in repeated cross-sectional cluster randomized trials.

PubMed

Nixon, R M; Thompson, S G

2003-09-15

Analysis of covariance models, which adjust for a baseline covariate, are often used to compare treatment groups in a controlled trial in which individuals are randomized. Such analysis adjusts for any baseline imbalance and usually increases the precision of the treatment effect estimate. We assess the value of such adjustments in the context of a cluster randomized trial with repeated cross-sectional design and a binary outcome. In such a design, a new sample of individuals is taken from the clusters at each measurement occasion, so that baseline adjustment has to be at the cluster level. Logistic regression models are used to analyse the data, with cluster level random effects to allow for different outcome probabilities in each cluster. We compare the estimated treatment effect and its precision in models that incorporate a covariate measuring the cluster level probabilities at baseline and those that do not. In two data sets, taken from a cluster randomized trial in the treatment of menorrhagia, the value of baseline adjustment is only evident when the number of subjects per cluster is large. We assess the generalizability of these findings by undertaking a simulation study, and find that increased precision of the treatment effect requires both large cluster sizes and substantial heterogeneity between clusters at baseline, but baseline imbalance arising by chance in a randomized study can always be effectively adjusted for. Copyright 2003 John Wiley & Sons, Ltd.

Estimating network effect in geocenter motion: Theory

NASA Astrophysics Data System (ADS)

Zannat, Umma Jamila; Tregoning, Paul

2017-10-01

Geophysical models and their interpretations of several processes of interest, such as sea level rise, postseismic relaxation, and glacial isostatic adjustment, are intertwined with the need to realize the International Terrestrial Reference Frame. However, this realization needs to take into account the geocenter motion, that is, the motion of the center of figure of the Earth surface, due to, for example, deformation of the surface by earthquakes or hydrological loading effects. Usually, there is also a discrepancy, known as the network effect, between the theoretically convenient center of figure and the physically accessible center of network frames, because of unavoidable factors such as uneven station distribution, lack of stations in the oceans, disparity in the coverage between the two hemispheres, and the existence of tectonically deforming zones. Here we develop a method to estimate the magnitude of the network effect, that is, the error introduced by the incomplete sampling of the Earth surface, in measuring the geocenter motion, for a network of space geodetic stations of a fixed size N. For this purpose, we use, as our proposed estimate, the standard deviations of the changes in Helmert parameters measured by a random network of the same size N. We show that our estimate scales as 1/√N and give an explicit formula for it in terms of the vector spherical harmonics expansion of the displacement field. In a complementary paper we apply this formalism to coseismic displacements and elastic deformations due to surface water movements.

The stress-buffering effects of hope on adjustment to multiple sclerosis.

PubMed

Madan, Sindia; Pakenham, Kenneth I

2014-12-01

Hope is an important resource for coping with chronic illness; however, the role of hope in adjusting to multiple sclerosis (MS) has been neglected, and the mechanisms by which hope exerts beneficial impacts are not well understood. This study aims to examine the direct and stress-moderating effects of dispositional hope and its components (agency and pathways) on adjustment to MS. A total of 296 people with MS completed questionnaires at time 1 at 12 months later and time 2. Focal predictors were stress, hope, agency and pathways, and the adjustment outcomes were anxiety, depression, positive affect, positive states of mind and life satisfaction. Results of regression analyses showed that as predicted, greater hope was associated with better adjustment after controlling for the effects of time 1 adjustment and relevant demographics and illness variables. However, these direct effects of hope were subsumed by stress-buffering effects. Regarding the hope components, the beneficial impacts of agency emerged via a direct effects mechanism, whereas the effects of pathways were evidenced via a moderating mechanism. Findings highlight hope as an important protective coping resource for coping with MS and accentuate the roles of both agency and pathways thinking and their different modes of influence in this process.

Alternative evaluation metrics for risk adjustment methods.

PubMed

Park, Sungchul; Basu, Anirban

2018-06-01

Risk adjustment is instituted to counter risk selection by accurately equating payments with expected expenditures. Traditional risk-adjustment methods are designed to estimate accurate payments at the group level. However, this generates residual risks at the individual level, especially for high-expenditure individuals, thereby inducing health plans to avoid those with high residual risks. To identify an optimal risk-adjustment method, we perform a comprehensive comparison of prediction accuracies at the group level, at the tail distributions, and at the individual level across 19 estimators: 9 parametric regression, 7 machine learning, and 3 distributional estimators. Using the 2013-2014 MarketScan database, we find that no one estimator performs best in all prediction accuracies. Generally, machine learning and distribution-based estimators achieve higher group-level prediction accuracy than parametric regression estimators. However, parametric regression estimators show higher tail distribution prediction accuracy and individual-level prediction accuracy, especially at the tails of the distribution. This suggests that there is a trade-off in selecting an appropriate risk-adjustment method between estimating accurate payments at the group level and lower residual risks at the individual level. Our results indicate that an optimal method cannot be determined solely on the basis of statistical metrics but rather needs to account for simulating plans' risk selective behaviors. Copyright © 2018 John Wiley & Sons, Ltd.

Adjusting for publication biases across similar interventions performed well when compared with gold standard data.

PubMed

Moreno, Santiago G; Sutton, Alex J; Ades, A E; Cooper, Nicola J; Abrams, Keith R

2011-11-01

To extend, apply, and evaluate a regression-based approach to adjusting meta-analysis for publication and related biases. The approach uses related meta-analyses to improve estimation by borrowing strength on the degree of bias. The proposed adjustment approach is described. Adjustments are applied both independently and by borrowing strength across journal-extracted data on the effectiveness of 12 antidepressant drugs from placebo-controlled trials. The methods are also applied to Food and Drug Administration (FDA) data obtained on the same 12 drugs. Results are compared, viewing the FDA observed data as gold standard. Estimates adjusted for publication biases made independently for each drug were very uncertain using both the journal and FDA data. Adjusted estimates were much more precise when borrowing strength across meta-analyses. Reassuringly, adjustments in this way made to the journal data agreed closely with the observed estimates from the FDA data, while the adjusted FDA results changed only minimally from those observed from the FDA data. The method worked well in the case study considered and therefore further evaluation is encouraged. It is suggested that this approach may be especially useful when adjusting several meta-analyses on similar interventions and outcomes, particularly when there are small numbers of studies. Copyright © 2011 Elsevier Inc. All rights reserved.

Tamoxifen for breast cancer risk reduction: impact of alternative approaches to quality-of-life adjustment on cost-effectiveness analysis.

PubMed

Melnikow, Joy; Birch, Stephen; Slee, Christina; McCarthy, Theodore J; Helms, L Jay; Kuppermann, Miriam

2008-09-01

In cost-effectiveness analysis (CEA), the effects of health-care interventions on multiple health dimensions typically require consideration of both quantity and quality of life. To explore the impact of alternative approaches to quality-of-life adjustment using patient preferences (utilities) on the outcome of a CEA on use of tamoxifen for breast cancer risk reduction. A state transition Markov model tracked hypothetical cohorts of women who did or did not take 5 years of tamoxifen for breast cancer risk reduction. Incremental quality-adjusted effectiveness and cost-effectiveness ratios (ICERs) for models including and excluding a utility adjustment for menopausal symptoms were compared with each other and to a global utility model. Two hundred fifty-five women aged 50 and over with estimated 5-year breast cancer risk >or=1.67% participated in utility assessment interviews. Standard gamble utilities were assessed for specified tamoxifen-related health outcomes, current health, and for a global assessment of possible outcomes of tamoxifen use. Inclusion of a utility for menopausal symptoms in the outcome-specific models substantially increased the ICER; at the threshold 5-year breast cancer risk of 1.67%, tamoxifen was dominated. When a global utility for tamoxifen was used in place of outcome-specific utilities, tamoxifen was dominated under all circumstances. CEAs may be profoundly affected by the types of outcomes considered for quality-of-life adjustment and how these outcomes are grouped for utility assessment. Comparisons of ICERs across analyses must consider effects of different approaches to using utilities for quality-of-life adjustment.

Individual and crossover effects of stress on adjustment in medical student marriages.

PubMed

Katz, J; Monnier, J; Libet, J; Shaw, D; Beach, S R

2000-07-01

High-stress individuals may benefit from social support, although their support providers may be adversely affected via stress crossover effects. Individual and crossover effects of perceived stress within medical student marriages (n = 30) were investigated. Perceived spousal support was positively associated with individuals' own marital and emotional adjustment, attenuating stress effects. With regard to crossover effects, medical students' perceived stress was significantly associated with their spouses' emotional adjustment. Further, medical students' own emotional adjustment fully mediated this crossover effect. Results suggest that the contagion of negative affect may serve as a key mechanism through which stress crossover effects operate in marriage.

Diagnostic Risk Adjustment for Medicaid: The Disability Payment System

PubMed Central

Kronick, Richard; Dreyfus, Tony; Lee, Lora; Zhou, Zhiyuan

1996-01-01

This article describes a system of diagnostic categories that Medicaid programs can use for adjusting capitation payments to health plans that enroll people with disability. Medicaid claims from Colorado, Michigan, Missouri, New York, and Ohio are analyzed to demonstrate that the greater predictability of costs among people with disabilities makes risk adjustment more feasible than for a general population and more critical to creating health systems for people with disability. The application of our diagnostic categories to State claims data is described, including estimated effects on subsequent-year costs of various diagnoses. The challenges of implementing adjustment by diagnosis are explored. PMID:10172665

Consequences of self-handicapping: effects on coping, academic performance, and adjustment.

PubMed

Zuckerman, M; Kieffer, S C; Knee, C R

1998-06-01

Self-handicappers erect impediments to performance to protect their self-esteem. The impediments may interfere with the ability to do well and, as such, may result in poor adjustment. Using a longitudinal design, the present studies examined prospective effects of self-handicapping on coping, academic performance, and several adjustment-related variables (e.g., self-esteem). It was found that, compared to low self-handicappers, high self-handicappers reported higher usage of coping strategies implying withdrawal and negative focus. High self-handicappers performed less well academically, an effect that was mediated in part by poor study habits. Finally, high self-handicapping resulted in poorer adjustment over time, and poorer adjustment resulted in higher self-handicapping over time. These relations are consistent with the idea of a vicious cycle in which self-handicapping and poor adjustment reinforce one another.

Estimated Short-Term Effects of Coarse Particles on Daily Mortality in Stockholm, Sweden

PubMed Central

Johansson, Christer; Forsberg, Bertil

2011-01-01

Background: Although serious health effects associated with particulate matter (PM) with aerodynamic diameter ≤ 10 μm (PM10) and ≤ 2.5 μm (PM2.5; fine fraction) are documented in many studies, the effects of coarse PM (PM2.5–10) are still under debate. Objective: In this study, we estimated the effects of short-term exposure of PM2.5–10 on daily mortality in Stockholm, Sweden. Method: We collected data on daily mortality for the years 2000 through 2008. Concentrations of PM10, PM2.5, ozone, and carbon monoxide were measured simultaneously in central Stockholm. We used additive Poisson regression models to examine the association between daily mortality and PM2.5–10 on the day of death and the day before. Effect estimates were adjusted for other pollutants (two-pollutant models) during different seasons. Results: We estimated a 1.68% increase [95% confidence interval (CI): 0.20%, 3.15%] in daily mortality per 10-μg/m3 increase in PM2.5–10 (single-pollutant model). The association with PM2.5–10 was stronger for November through May, when road dust is most important (1.69% increase; 95% CI: 0.21%, 3.17%), compared with the rest of the year (1.31% increase; 95% CI: –2.08%, 4.70%), although the difference was not statistically significant. When adjusted for other pollutants, particularly PM2.5, the effect estimates per 10 μg/m3 for PM2.5–10 decreased slightly but were still higher than corresponding effect estimates for PM2.5. Conclusions: Our analysis shows an increase in daily mortality associated with elevated urban background levels of PM2.5–10. Regulation of PM2.5–10 should be considered, along with actions to specifically reduce PM2.5–10 emissions, especially road dust suspension, in cities. PMID:22182596

Inverse probability weighting for covariate adjustment in randomized studies

PubMed Central

Li, Xiaochun; Li, Lingling

2013-01-01

SUMMARY Covariate adjustment in randomized clinical trials has the potential benefit of precision gain. It also has the potential pitfall of reduced objectivity as it opens the possibility of selecting “favorable” model that yields strong treatment benefit estimate. Although there is a large volume of statistical literature targeting on the first aspect, realistic solutions to enforce objective inference and improve precision are rare. As a typical randomized trial needs to accommodate many implementation issues beyond statistical considerations, maintaining the objectivity is at least as important as precision gain if not more, particularly from the perspective of the regulatory agencies. In this article, we propose a two-stage estimation procedure based on inverse probability weighting to achieve better precision without compromising objectivity. The procedure is designed in a way such that the covariate adjustment is performed before seeing the outcome, effectively reducing the possibility of selecting a “favorable” model that yields a strong intervention effect. Both theoretical and numerical properties of the estimation procedure are presented. Application of the proposed method to a real data example is presented. PMID:24038458

Smooth individual level covariates adjustment in disease mapping.

PubMed

Huque, Md Hamidul; Anderson, Craig; Walton, Richard; Woolford, Samuel; Ryan, Louise

2018-05-01

Spatial models for disease mapping should ideally account for covariates measured both at individual and area levels. The newly available "indiCAR" model fits the popular conditional autoregresssive (CAR) model by accommodating both individual and group level covariates while adjusting for spatial correlation in the disease rates. This algorithm has been shown to be effective but assumes log-linear associations between individual level covariates and outcome. In many studies, the relationship between individual level covariates and the outcome may be non-log-linear, and methods to track such nonlinearity between individual level covariate and outcome in spatial regression modeling are not well developed. In this paper, we propose a new algorithm, smooth-indiCAR, to fit an extension to the popular conditional autoregresssive model that can accommodate both linear and nonlinear individual level covariate effects while adjusting for group level covariates and spatial correlation in the disease rates. In this formulation, the effect of a continuous individual level covariate is accommodated via penalized splines. We describe a two-step estimation procedure to obtain reliable estimates of individual and group level covariate effects where both individual and group level covariate effects are estimated separately. This distributed computing framework enhances its application in the Big Data domain with a large number of individual/group level covariates. We evaluate the performance of smooth-indiCAR through simulation. Our results indicate that the smooth-indiCAR method provides reliable estimates of all regression and random effect parameters. We illustrate our proposed methodology with an analysis of data on neutropenia admissions in New South Wales (NSW), Australia. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

42 CFR 412.525 - Adjustments to the Federal prospective payment.

Code of Federal Regulations, 2010 CFR

2010-10-01

... its estimated costs for a patient exceed the adjusted LTC-MS-DRG payment plus a fixed-loss amount. For...-DRG relative weights that are in effect at the start of the applicable long-term care hospital...

A bias-adjusted evidence synthesis of RCT and observational data: the case of total hip replacement.

PubMed

Schnell-Inderst, Petra; Iglesias, Cynthia P; Arvandi, Marjan; Ciani, Oriana; Matteucci Gothe, Raffaella; Peters, Jaime; Blom, Ashley W; Taylor, Rod S; Siebert, Uwe

2017-02-01

Evaluation of clinical effectiveness of medical devices differs in some aspects from the evaluation of pharmaceuticals. One of the main challenges identified is lack of robust evidence and a will to make use of experimental and observational studies (OSs) in quantitative evidence synthesis accounting for internal and external biases. Using a case study of total hip replacement to compare the risk of revision of cemented and uncemented implant fixation modalities, we pooled treatment effect estimates from OS and RCTs, and simplified existing methods for bias-adjusted evidence synthesis to enhance practical application. We performed an elicitation exercise using methodological and clinical experts to determine the strength of beliefs about the magnitude of internal and external bias affecting estimates of treatment effect. We incorporated the bias-adjusted treatment effects into a generalized evidence synthesis, calculating both frequentist and Bayesian statistical models. We estimated relative risks as summary effect estimates with 95% confidence/credibility intervals to capture uncertainty. When we compared alternative approaches to synthesizing evidence, we found that the pooled effect size strongly depended on the inclusion of observational data as well as on the use bias-adjusted estimates. We demonstrated the feasibility of using observational studies in meta-analyses to complement RCTs and incorporate evidence from a wider spectrum of clinically relevant studies and healthcare settings. To ensure internal validity, OS data require sufficient correction for confounding and selection bias, either through study design and primary analysis, or by applying post-hoc bias adjustments to the results. © 2017 The Authors. Health Economics published by John Wiley & Sons, Ltd. © 2017 The Authors. Health Economics published by John Wiley & Sons, Ltd.

Money illusion among health care providers: should we adjust for inflation in analyses of provider behavior?

PubMed

Mayer, M L; Rozier, R G

2000-08-01

This analysis questions the appropriateness of inflation adjustment in analyses of provider behavior by comparing results from estimations using adjusted financial variables with those from estimations using unadjusted financial variables. Using Medicaid claims from 1984-1991, we explored the effects of Medicaid reimbursement increases on dentists' participation. Using results from inflation adjusted analyses, we would conclude that a 23% nominal increase in Medicaid reimbursement rates yields no increase in the number of Medicaid children seen by dentists. In contrast, estimations based on unadjusted reimbursement rates suggest that this same 23% nominal increase in reimbursement leads to an expected 16-person (15.4%) increase in the number of Medicaid patients seen per provider per year. These analyses demonstrate that results are sensitive to adjustment for inflation. While adjusting for inflation is a generally accepted practice in health services research, doing so without evidence that providers respond to adjusted reimbursement may be unjustified. More research is needed to determine the appropriateness of inflation adjustment in analyses of provider behavior, and the circumstances under which it should or should not be done.

Estimating contribution of anthocyanin pigments to osmotic adjustment during winter leaf reddening.

PubMed

Hughes, Nicole M; Carpenter, Kaylyn L; Cannon, Jonathan G

2013-01-15

The association between plant water stress and synthesis of red, anthocyanin pigments in leaves has led some plant biologists to propose an osmotic function of leaf reddening. According to this hypothesis, anthocyanins function as a solute in osmotic adjustment (OA), contributing to depression of osmotic potential (Ψ(π)) and maintenance of turgor pressure during drought-stressed conditions. Here we calculate the percent contribution of anthocyanin to leaf Ψ(π) during OA in two angiosperm evergreen species, Galax urceolata and Gaultheria procumbens. Both species exhibit dramatic leaf reddening under high light during winter, concomitant with declines in leaf water potential and accumulation of solutes. Data previously published by the authors on osmotic potential at full turgor (Ψ(π,100)) of G. urceolata and G. procumbens leaves before and after leaf reddening were used to estimate OA. In vivo molar concentrations of anthocyanin, glucose, fructose, and sucrose measured from the same individuals were converted to pressure equivalents using the Ideal Gas Law, and percent contribution to OA was estimated. Estimated mean OA during winter was -0.7MPa for G. urceolata and -0.8MPa for G. procumbens. In vivo concentrations of anthocyanin (3-10mM) were estimated to account for ∼2% of OA during winter, and comprised <0.7% of Ψ(π,100) in both species. Glucose, fructose, and sucrose combined accounted for roughly 50 and 80% of OA for G. urceolata and G. procumbens, respectively, and comprised ∼20% of Ψ(π,100). We observed that a co-occurring, acyanic species (Vinca minor) achieved similar OA without synthesizing anthocyanin. We conclude that anthocyanins represent a measurable, albeit meager, component of OA in red-leafed evergreen species during winter. However, due to their low concentrations, metabolic costliness relative to other osmolytes, and striking red color (unnecessary for an osmotic function), it is unlikely that they are synthesized solely for an

REFAME: Rain Estimation Using Forward Adjusted-Advection of Microwave Estimates

NASA Technical Reports Server (NTRS)

Behrangi, Ali; Imam, Bisher; Hsu, Kuolin; Sorooshian, Soroosh; Bellerby, Timothy J.

2009-01-01

Sensors flying on satellites provide the only practical means of estimating the precipitation that falls over the entire globe, particularly across the vast unpopulated expanses of Earth s oceans. The sensors that observe the Earth using microwave frequencies provide the best data, but currently these are mounted only on satellites flying in "low Earth orbit". Such satellites constantly move across the Earth s surface, providing snapshots of any given location every 12-36 hours. The entire constellation of low-orbit satellites numbers less than a dozen, and their orbits are not coordinated, so a location will frequently go two or more hours between snapshots. "Geosynchronous Earth orbit" (GEO) satellites continuously observe the same region of the globe, allowing them to provide very frequent pictures. For example, the "satellite movies" shown on television come from GEO satellites. However, the sensors available on GEO satellites cannot match the skill of the low-orbit microwave sensors in estimating precipitation. It is perhaps obvious that scientists should try to combine these very different kinds of data, taking advantage of the strengths of each, but this simple concept has proved to be a huge challenge. The scheme in this paper is "Lagrangian", meaning we follow the storm systems, rather than being tied to a fixed grid of boxes on the Earth s surface. Whenever a microwave snapshot occurs, we gladly use the resulting precipitation estimate. Then at all the times between the microwave snapshots we force the storm system to make a smooth transition from one snapshot s values to the next. We know that a lot more changes occur between the snapshots, but this smooth transition the best we can do with the microwave data alone. The key new contribution in this paper is that we also look at the relative variations in the GEO estimates during these in-between times and force the estimated changes in the precipitation to have similar variations. Preliminary testing

The impact of selection bias on vaccine effectiveness estimates from test-negative studies.

PubMed

Jackson, Michael L; Phillips, C Hallie; Benoit, Joyce; Kiniry, Erika; Madziwa, Lawrence; Nelson, Jennifer C; Jackson, Lisa A

2018-01-29

Estimates of vaccine effectiveness (VE) from test-negative studies may be subject to selection bias. In the context of influenza VE, we used simulations to identify situations in which meaningful selection bias can occur. We also analyzed observational study data for evidence of selection bias. For the simulation study, we defined a hypothetical population whose members are at risk for acute respiratory illness (ARI) due to influenza and other pathogens. An unmeasured "healthcare seeking proclivity" affects both probability of vaccination and probability of seeking care for an ARI. We varied the direction and magnitude of these effects and identified situations where meaningful bias occurred. For the observational study, we reanalyzed data from the United States Influenza VE Network, an ongoing test-negative study. We compared "bias-naïve" VE estimates to bias-adjusted estimates, which used data from the source populations to correct for sampling bias. In the simulation study, an unmeasured care-seeking proclivity could create selection bias if persons with influenza ARI were more (or less) likely to seek care than persons with non-influenza ARI. However, selection bias was only meaningful when rates of care seeking between influenza ARI and non-influenza ARI were very different. In the observational study, the bias-naïve VE estimate of 55% (95% CI, 47--62%) was trivially different from the bias-adjusted VE estimate of 57% (95% CI, 49--63%). In combination, these studies suggest that while selection bias is possible in test-negative VE studies, this bias in unlikely to be meaningful under conditions likely to be encountered in practice. Researchers and public health officials can continue to rely on VE estimates from test-negative studies. Copyright © 2017 Elsevier Ltd. All rights reserved.

Optimizing ACS NSQIP modeling for evaluation of surgical quality and risk: patient risk adjustment, procedure mix adjustment, shrinkage adjustment, and surgical focus.

PubMed

Cohen, Mark E; Ko, Clifford Y; Bilimoria, Karl Y; Zhou, Lynn; Huffman, Kristopher; Wang, Xue; Liu, Yaoming; Kraemer, Kari; Meng, Xiangju; Merkow, Ryan; Chow, Warren; Matel, Brian; Richards, Karen; Hart, Amy J; Dimick, Justin B; Hall, Bruce L

2013-08-01

The American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) collects detailed clinical data from participating hospitals using standardized data definitions, analyzes these data, and provides participating hospitals with reports that permit risk-adjusted comparisons with a surgical quality standard. Since its inception, the ACS NSQIP has worked to refine surgical outcomes measurements and enhance statistical methods to improve the reliability and validity of this hospital profiling. From an original focus on controlling for between-hospital differences in patient risk factors with logistic regression, ACS NSQIP has added a variable to better adjust for the complexity and risk profile of surgical procedures (procedure mix adjustment) and stabilized estimates derived from small samples by using a hierarchical model with shrinkage adjustment. New models have been developed focusing on specific surgical procedures (eg, "Procedure Targeted" models), which provide opportunities to incorporate indication and other procedure-specific variables and outcomes to improve risk adjustment. In addition, comparative benchmark reports given to participating hospitals have been expanded considerably to allow more detailed evaluations of performance. Finally, procedures have been developed to estimate surgical risk for individual patients. This article describes the development of, and justification for, these new statistical methods and reporting strategies in ACS NSQIP. Copyright © 2013 American College of Surgeons. Published by Elsevier Inc. All rights reserved.

The effects of coping on adjustment: Re-examining the goodness of fit model of coping effectiveness.

PubMed

Masel, C N; Terry, D J; Gribble, M

1996-01-01

Abstract The primary aim of the present study was to examine the extent to which the effects of coping on adjustment are moderated by levels of event controllability. Specifically, the research tested two revisions to the goodness of fit model of coping effectiveness. First, it was hypothesized that the effects of problem management coping (but not problem appraisal coping) would be moderated by levels of event controllability. Second, it was hypothesized that the effects of emotion-focused coping would be moderated by event controllability, but only in the acute phase of a stressful encounter. To test these predictions, a longitudinal study was undertaken (185 undergraduate students participated in all three stages of the research). Measures of initial adjustment (low depression and coping efficacy) were obtained at Time 1. Four weeks later (Time 2), coping responses to a current or a recent stressor were assessed. Based on subjects' descriptions of the event, objective and subjective measures of event controllability were also obtained. Measures of concurrent and subsequent adjustment were obtained at Times 2 and 3 (two weeks later), respectively. There was only weak support for the goodness of fit model of coping effectiveness. The beneficial effects of a high proportion of problem management coping (relative to total coping efforts) on Time 3 perceptions of coping efficacy were more evident in high control than in low control situations. Other results of the research revealed that, irrespective of the controllability of the event, problem appraisal coping strategies and emotion-focused strategies (escapism and self-denigration) were associated with high and low levels of concurrent adjustment, respectively. The effects of these coping responses on subsequent adjustment were mediated through concurrent levels of adjustment.

Estimates of Pandemic Influenza Vaccine Effectiveness in Europe, 2009–2010: Results of Influenza Monitoring Vaccine Effectiveness in Europe (I-MOVE) Multicentre Case-Control Study

PubMed Central

Valenciano, Marta; Kissling, Esther; Cohen, Jean-Marie; Oroszi, Beatrix; Barret, Anne-Sophie; Rizzo, Caterina; Nunes, Baltazar; Pitigoi, Daniela; Larrauri Cámara, Amparro; Mosnier, Anne; Horvath, Judith K.; O'Donnell, Joan; Bella, Antonino; Guiomar, Raquel; Lupulescu, Emilia; Savulescu, Camelia; Ciancio, Bruno C.; Kramarz, Piotr; Moren, Alain

2011-01-01

Background A multicentre case-control study based on sentinel practitioner surveillance networks from seven European countries was undertaken to estimate the effectiveness of 2009–2010 pandemic and seasonal influenza vaccines against medically attended influenza-like illness (ILI) laboratory-confirmed as pandemic influenza A (H1N1) (pH1N1). Methods and Findings Sentinel practitioners swabbed ILI patients using systematic sampling. We included in the study patients meeting the European ILI case definition with onset of symptoms >14 days after the start of national pandemic vaccination campaigns. We compared pH1N1 cases to influenza laboratory-negative controls. A valid vaccination corresponded to >14 days between receiving a dose of vaccine and symptom onset. We estimated pooled vaccine effectiveness (VE) as 1 minus the odds ratio with the study site as a fixed effect. Using logistic regression, we adjusted VE for potential confounding factors (age group, sex, month of onset, chronic diseases and related hospitalizations, smoking history, seasonal influenza vaccinations, practitioner visits in previous year). We conducted a complete case analysis excluding individuals with missing values and a multiple multivariate imputation to estimate missing values. The multivariate imputation (n = 2902) adjusted pandemic VE (PIVE) estimates were 71.9% (95% confidence interval [CI] 45.6–85.5) overall; 78.4% (95% CI 54.4–89.8) in patients <65 years; and 72.9% (95% CI 39.8–87.8) in individuals without chronic disease. The complete case (n = 1,502) adjusted PIVE were 66.0% (95% CI 23.9–84.8), 71.3% (95% CI 29.1–88.4), and 70.2% (95% CI 19.4–89.0), respectively. The adjusted PIVE was 66.0% (95% CI −69.9 to 93.2) if vaccinated 8–14 days before ILI onset. The adjusted 2009–2010 seasonal influenza VE was 9.9% (95% CI −65.2 to 50.9). Conclusions Our results suggest good protection of the pandemic monovalent vaccine against medically attended pH1N1 and no

Inverse probability weighting for covariate adjustment in randomized studies.

PubMed

Shen, Changyu; Li, Xiaochun; Li, Lingling

2014-02-20

Covariate adjustment in randomized clinical trials has the potential benefit of precision gain. It also has the potential pitfall of reduced objectivity as it opens the possibility of selecting a 'favorable' model that yields strong treatment benefit estimate. Although there is a large volume of statistical literature targeting on the first aspect, realistic solutions to enforce objective inference and improve precision are rare. As a typical randomized trial needs to accommodate many implementation issues beyond statistical considerations, maintaining the objectivity is at least as important as precision gain if not more, particularly from the perspective of the regulatory agencies. In this article, we propose a two-stage estimation procedure based on inverse probability weighting to achieve better precision without compromising objectivity. The procedure is designed in a way such that the covariate adjustment is performed before seeing the outcome, effectively reducing the possibility of selecting a 'favorable' model that yields a strong intervention effect. Both theoretical and numerical properties of the estimation procedure are presented. Application of the proposed method to a real data example is presented. Copyright © 2013 John Wiley & Sons, Ltd.

Enhanced Estimates of the Influenza Vaccination Effect in Preventing Mortality

PubMed Central

Castilla, Jesús; Guevara, Marcela; Martínez-Baz, Iván; Ezpeleta, Carmen; Delfrade, Josu; Irisarri, Fátima; Moreno-Iribas, Conchi

2015-01-01

Abstract Mortality is a major end-point in the evaluation of influenza vaccine effectiveness. However, this effect is not well known, since most previous studies failed to show good control of biases. We aimed to estimate the effectiveness of influenza vaccination in preventing all-cause mortality in community-dwelling seniors. Since 2009, a population-based cohort study using healthcare databases has been conducted in Navarra, Spain. In 2 late influenza seasons, 2011/2012 and 2012/2013, all-cause mortality in the period January to May was compared between seniors (65 years or over) who received the trivalent influenza vaccine and those who were unvaccinated, adjusting for demographics, major chronic conditions, dependence, previous hospitalization, and pneumococcal vaccination. The cohort included 103,156 seniors in the 2011/2012 season and 105,140 in the 2012/2013 season (58% vaccinated). Seniors vaccinated in the previous season who discontinued vaccination (6% of the total) had excess mortality and were excluded to prevent frailty bias. The final analysis included 80,730 person-years and 2778 deaths. Vaccinated seniors had 16% less all-cause mortality than those unvaccinated (adjusted rate ratio [RR] = 0.84; 95% confidence interval 0.76–0.93). This association disappeared in the post-influenza period (adjusted RR = 0.96; 95% confidence interval 0.85–1.09). A similar comparison did not find an association in January to May of the 2009/2010 pandemic season (adjusted RR = 0.98; 95% confidence interval 0.84–1.14), when no effect of the seasonal vaccine was expected. On average, 1 death was prevented for every 328 seniors vaccinated: 1 for every 649 in the 65 to 74 year age group and 1 for every 251 among those aged 75 and over. These results suggest a moderate preventive effect and a high potential impact of the seasonal influenza vaccine against all-cause mortality. This reinforces the recommendation of annual influenza vaccination in seniors

Regression estimators for generic health-related quality of life and quality-adjusted life years.

PubMed

Basu, Anirban; Manca, Andrea

2012-01-01

To develop regression models for outcomes with truncated supports, such as health-related quality of life (HRQoL) data, and account for features typical of such data such as a skewed distribution, spikes at 1 or 0, and heteroskedasticity. Regression estimators based on features of the Beta distribution. First, both a single equation and a 2-part model are presented, along with estimation algorithms based on maximum-likelihood, quasi-likelihood, and Bayesian Markov-chain Monte Carlo methods. A novel Bayesian quasi-likelihood estimator is proposed. Second, a simulation exercise is presented to assess the performance of the proposed estimators against ordinary least squares (OLS) regression for a variety of HRQoL distributions that are encountered in practice. Finally, the performance of the proposed estimators is assessed by using them to quantify the treatment effect on QALYs in the EVALUATE hysterectomy trial. Overall model fit is studied using several goodness-of-fit tests such as Pearson's correlation test, link and reset tests, and a modified Hosmer-Lemeshow test. The simulation results indicate that the proposed methods are more robust in estimating covariate effects than OLS, especially when the effects are large or the HRQoL distribution has a large spike at 1. Quasi-likelihood techniques are more robust than maximum likelihood estimators. When applied to the EVALUATE trial, all but the maximum likelihood estimators produce unbiased estimates of the treatment effect. One and 2-part Beta regression models provide flexible approaches to regress the outcomes with truncated supports, such as HRQoL, on covariates, after accounting for many idiosyncratic features of the outcomes distribution. This work will provide applied researchers with a practical set of tools to model outcomes in cost-effectiveness analysis.

[Health-based risk adjustment. Effects and side effects].

PubMed

Jahn, R; Schillo, S; Wasem, J

2012-05-01

Numerous health systems have introduced competition between health plans while banning risk-rated premiums. Risk adjustment for health plans is introduced to reduce incentives for risk selection and to create incentives for health plans to permanently invest in care for the chronically ill. According to the international health economics state of the art, risk adjustment in the German social health insurance system has used information on health status (measured by diagnoses and drug prescriptions) on top of demographic information since 2009. In non-competitive health care systems similar mechanisms are sometimes established, e.g. to achieve an equitable distribution of resources between regions. An evaluation of the first year of health-based risk adjustment demonstrates a superior performance in comparison to the old, demographic risk adjustment. The old risk adjustment formula (without ex post high-cost pooling) showed R(2) of 5.8%, CPM of 10.4% and MAPE of 2,226 €, in contrast to the new health status-based risk adjustment formula (without cash benefit for sick allowance) which reaches R(2) 20.2%, CPM 22.5% and MAPE 1,817 €. However, to make competition between health plans functional for improvement of quality and efficiency of health care, health plans must be granted additional instruments to act as prudent buyers of health care.

A regression-adjusted approach can estimate competing biomass

Treesearch

James H. Miller

1983-01-01

A method is presented for estimating above-ground herbaceous and woody biomass on competition research plots. On a set of destructively-sampled plots, an ocular estimate of biomass by vegetative component is first made, after which vegetation is clipped, dried, and weighed. Linear regressions are then calculated for each component between estimated and actual weights...

Using Audit Information to Adjust Parameter Estimates for Data Errors in Clinical Trials

PubMed Central

Shepherd, Bryan E.; Shaw, Pamela A.; Dodd, Lori E.

2013-01-01

Background Audits are often performed to assess the quality of clinical trial data, but beyond detecting fraud or sloppiness, the audit data is generally ignored. In earlier work using data from a non-randomized study, Shepherd and Yu (2011) developed statistical methods to incorporate audit results into study estimates, and demonstrated that audit data could be used to eliminate bias. Purpose In this manuscript we examine the usefulness of audit-based error-correction methods in clinical trial settings where a continuous outcome is of primary interest. Methods We demonstrate the bias of multiple linear regression estimates in general settings with an outcome that may have errors and a set of covariates for which some may have errors and others, including treatment assignment, are recorded correctly for all subjects. We study this bias under different assumptions including independence between treatment assignment, covariates, and data errors (conceivable in a double-blinded randomized trial) and independence between treatment assignment and covariates but not data errors (possible in an unblinded randomized trial). We review moment-based estimators to incorporate the audit data and propose new multiple imputation estimators. The performance of estimators is studied in simulations. Results When treatment is randomized and unrelated to data errors, estimates of the treatment effect using the original error-prone data (i.e., ignoring the audit results) are unbiased. In this setting, both moment and multiple imputation estimators incorporating audit data are more variable than standard analyses using the original data. In contrast, in settings where treatment is randomized but correlated with data errors and in settings where treatment is not randomized, standard treatment effect estimates will be biased. And in all settings, parameter estimates for the original, error-prone covariates will be biased. Treatment and covariate effect estimates can be corrected by

On the Effects of Wives' Employment on Marital Adjustment and Companionship.

ERIC Educational Resources Information Center

Locksley, Anne

1980-01-01

No evidence was found for any effect of wives' employment or degree of interest in their work activity on marital adjustment and companionship. The extensive controversy over wives' increasing labor-force participation has resulted from unwarranted assumptions about the impact of wives' working on marital adjustment. (Author)

Modeling Quality-Adjusted Life Expectancy Loss Resulting from Tobacco Use in the United States

ERIC Educational Resources Information Center

Kaplan, Robert M.; Anderson, John P.; Kaplan, Cameron M.

2007-01-01

Purpose: To describe the development of a model for estimating the effects of tobacco use upon Quality Adjusted Life Years (QALYs) and to estimate the impact of tobacco use on health outcomes for the United States (US) population using the model. Method: We obtained estimates of tobacco consumption from 6 years of the National Health Interview…

Adjusting Estimates of the Expected Value of Information for Implementation: Theoretical Framework and Practical Application.

PubMed

Andronis, Lazaros; Barton, Pelham M

2016-04-01

Value of information (VoI) calculations give the expected benefits of decision making under perfect information (EVPI) or sample information (EVSI), typically on the premise that any treatment recommendations made in light of this information will be implemented instantly and fully. This assumption is unlikely to hold in health care; evidence shows that obtaining further information typically leads to "improved" rather than "perfect" implementation. To present a method of calculating the expected value of further research that accounts for the reality of improved implementation. This work extends an existing conceptual framework by introducing additional states of the world regarding information (sample information, in addition to current and perfect information) and implementation (improved implementation, in addition to current and optimal implementation). The extension allows calculating the "implementation-adjusted" EVSI (IA-EVSI), a measure that accounts for different degrees of implementation. Calculations of implementation-adjusted estimates are illustrated under different scenarios through a stylized case study in non-small cell lung cancer. In the particular case study, the population values for EVSI and IA-EVSI were £ 25 million and £ 8 million, respectively; thus, a decision assuming perfect implementation would have overestimated the expected value of research by about £ 17 million. IA-EVSI was driven by the assumed time horizon and, importantly, the specified rate of change in implementation: the higher the rate, the greater the IA-EVSI and the lower the difference between IA-EVSI and EVSI. Traditionally calculated measures of population VoI rely on unrealistic assumptions about implementation. This article provides a simple framework that accounts for improved, rather than perfect, implementation and offers more realistic estimates of the expected value of research. © The Author(s) 2015.

Analysis of Longitudinal Studies With Repeated Outcome Measures: Adjusting for Time-Dependent Confounding Using Conventional Methods.

PubMed

Keogh, Ruth H; Daniel, Rhian M; VanderWeele, Tyler J; Vansteelandt, Stijn

2018-05-01

Estimation of causal effects of time-varying exposures using longitudinal data is a common problem in epidemiology. When there are time-varying confounders, which may include past outcomes, affected by prior exposure, standard regression methods can lead to bias. Methods such as inverse probability weighted estimation of marginal structural models have been developed to address this problem. However, in this paper we show how standard regression methods can be used, even in the presence of time-dependent confounding, to estimate the total effect of an exposure on a subsequent outcome by controlling appropriately for prior exposures, outcomes, and time-varying covariates. We refer to the resulting estimation approach as sequential conditional mean models (SCMMs), which can be fitted using generalized estimating equations. We outline this approach and describe how including propensity score adjustment is advantageous. We compare the causal effects being estimated using SCMMs and marginal structural models, and we compare the two approaches using simulations. SCMMs enable more precise inferences, with greater robustness against model misspecification via propensity score adjustment, and easily accommodate continuous exposures and interactions. A new test for direct effects of past exposures on a subsequent outcome is described.

Adjusted peak-flow frequency estimates for selected streamflow-gaging stations in or near Montana based on data through water year 2011: Chapter D in Montana StreamStats

USGS Publications Warehouse

Sando, Steven K.; Sando, Roy; McCarthy, Peter M.; Dutton, DeAnn M.

2016-04-05

The climatic conditions of the specific time period during which peak-flow data were collected at a given streamflow-gaging station (hereinafter referred to as gaging station) can substantially affect how well the peak-flow frequency (hereinafter referred to as frequency) results represent long-term hydrologic conditions. Differences in the timing of the periods of record can result in substantial inconsistencies in frequency estimates for hydrologically similar gaging stations. Potential for inconsistency increases with decreasing peak-flow record length. The representativeness of the frequency estimates for a short-term gaging station can be adjusted by various methods including weighting the at-site results in association with frequency estimates from regional regression equations (RREs) by using the Weighted Independent Estimates (WIE) program. Also, for gaging stations that cannot be adjusted by using the WIE program because of regulation or drainage areas too large for application of RREs, frequency estimates might be improved by using record extension procedures, including a mixed-station analysis using the maintenance of variance type I (MOVE.1) procedure. The U.S. Geological Survey, in cooperation with the Montana Department of Transportation and the Montana Department of Natural Resources and Conservation, completed a study to provide adjusted frequency estimates for selected gaging stations through water year 2011.The purpose of Chapter D of this Scientific Investigations Report is to present adjusted frequency estimates for 504 selected streamflow-gaging stations in or near Montana based on data through water year 2011. Estimates of peak-flow magnitudes for the 66.7-, 50-, 42.9-, 20-, 10-, 4-, 2-, 1-, 0.5-, and 0.2-percent annual exceedance probabilities are reported. These annual exceedance probabilities correspond to the 1.5-, 2-, 2.33-, 5-, 10-, 25-, 50-, 100-, 200-, and 500-year recurrence intervals, respectively.The at-site frequency estimates were

Evaluation of energy balance closure adjustment methods by independent evapotranspiration estimates from lysimeters and hydrological simulations

DOE PAGES

Mauder, Matthias; Genzel, Sandra; Fu, Jin; ...

2017-11-10

Here, we report non-closure of the surface energy balance is a frequently observed phenomenon of hydrometeorological field measurements, when using the eddy-covariance method, which can be ascribed to an underestimation of the turbulent fluxes. Several approaches have been proposed in order to adjust the measured fluxes for this apparent systematic error. However, there are uncertainties about partitioning of the energy balance residual between the sensible and latent heat flux and whether such a correction should be applied on 30-minute data or longer time scales. The data for this study originate from two grassland sites in southern Germany, where measurements frommore » weighable lysimeters are available as reference. The adjusted evapotranspiration rates are also compared with joint energy and water balance simulations using a physically-based distributed hydrological model. We evaluate two adjustment methods: the first one preserves the Bowen ratio and the correction factor is determined on a daily basis. The second one attributes a smaller portion of the residual energy to the latent heat flux than to the sensible heat flux for closing the energy balance for every 30-minute flux integration interval. Both methods lead to an improved agreement of the eddy-covariance based fluxes with the independent lysimeter estimates and the physically-based model simulations. The first method results in a better comparability of evapotranspiration rates, and the second method leads to a smaller overall bias. These results are similar between both sites despite considerable differences in terrain complexity and grassland management. Moreover, we found that a daily adjustment factor leads to less scatter than a complete partitioning of the residual for every half-hour time interval. Lastly, the vertical temperature gradient in the surface layer and friction velocity were identified as important predictors for a potential future parameterization of the energy balance

Evaluation of energy balance closure adjustment methods by independent evapotranspiration estimates from lysimeters and hydrological simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mauder, Matthias; Genzel, Sandra; Fu, Jin

Here, we report non-closure of the surface energy balance is a frequently observed phenomenon of hydrometeorological field measurements, when using the eddy-covariance method, which can be ascribed to an underestimation of the turbulent fluxes. Several approaches have been proposed in order to adjust the measured fluxes for this apparent systematic error. However, there are uncertainties about partitioning of the energy balance residual between the sensible and latent heat flux and whether such a correction should be applied on 30-minute data or longer time scales. The data for this study originate from two grassland sites in southern Germany, where measurements frommore » weighable lysimeters are available as reference. The adjusted evapotranspiration rates are also compared with joint energy and water balance simulations using a physically-based distributed hydrological model. We evaluate two adjustment methods: the first one preserves the Bowen ratio and the correction factor is determined on a daily basis. The second one attributes a smaller portion of the residual energy to the latent heat flux than to the sensible heat flux for closing the energy balance for every 30-minute flux integration interval. Both methods lead to an improved agreement of the eddy-covariance based fluxes with the independent lysimeter estimates and the physically-based model simulations. The first method results in a better comparability of evapotranspiration rates, and the second method leads to a smaller overall bias. These results are similar between both sites despite considerable differences in terrain complexity and grassland management. Moreover, we found that a daily adjustment factor leads to less scatter than a complete partitioning of the residual for every half-hour time interval. Lastly, the vertical temperature gradient in the surface layer and friction velocity were identified as important predictors for a potential future parameterization of the energy balance

Consistency between satellite-derived and modeled estimates of the direct aerosol effect.

PubMed

Myhre, Gunnar

2009-07-10

In the Intergovernmental Panel on Climate Change Fourth Assessment Report, the direct aerosol effect is reported to have a radiative forcing estimate of -0.5 Watt per square meter (W m(-2)), offsetting the warming from CO2 by almost one-third. The uncertainty, however, ranges from -0.9 to -0.1 W m(-2), which is largely due to differences between estimates from global aerosol models and observation-based estimates, with the latter tending to have stronger (more negative) radiative forcing. This study demonstrates consistency between a global aerosol model and adjustment to an observation-based method, producing a global and annual mean radiative forcing that is weaker than -0.5 W m(-2), with a best estimate of -0.3 W m(-2). The physical explanation for the earlier discrepancy is that the relative increase in anthropogenic black carbon (absorbing aerosols) is much larger than the overall increase in the anthropogenic abundance of aerosols.

Singularity-sensitive gauge-based radar rainfall adjustment methods for urban hydrological applications

NASA Astrophysics Data System (ADS)

Wang, L.-P.; Ochoa-Rodríguez, S.; Onof, C.; Willems, P.

2015-09-01

Gauge-based radar rainfall adjustment techniques have been widely used to improve the applicability of radar rainfall estimates to large-scale hydrological modelling. However, their use for urban hydrological applications is limited as they were mostly developed based upon Gaussian approximations and therefore tend to smooth off so-called "singularities" (features of a non-Gaussian field) that can be observed in the fine-scale rainfall structure. Overlooking the singularities could be critical, given that their distribution is highly consistent with that of local extreme magnitudes. This deficiency may cause large errors in the subsequent urban hydrological modelling. To address this limitation and improve the applicability of adjustment techniques at urban scales, a method is proposed herein which incorporates a local singularity analysis into existing adjustment techniques and allows the preservation of the singularity structures throughout the adjustment process. In this paper the proposed singularity analysis is incorporated into the Bayesian merging technique and the performance of the resulting singularity-sensitive method is compared with that of the original Bayesian (non singularity-sensitive) technique and the commonly used mean field bias adjustment. This test is conducted using as case study four storm events observed in the Portobello catchment (53 km2) (Edinburgh, UK) during 2011 and for which radar estimates, dense rain gauge and sewer flow records, as well as a recently calibrated urban drainage model were available. The results suggest that, in general, the proposed singularity-sensitive method can effectively preserve the non-normality in local rainfall structure, while retaining the ability of the original adjustment techniques to generate nearly unbiased estimates. Moreover, the ability of the singularity-sensitive technique to preserve the non-normality in rainfall estimates often leads to better reproduction of the urban drainage system

Adjusted adaptive Lasso for covariate model-building in nonlinear mixed-effect pharmacokinetic models.

PubMed

Haem, Elham; Harling, Kajsa; Ayatollahi, Seyyed Mohammad Taghi; Zare, Najaf; Karlsson, Mats O

2017-02-01

One important aim in population pharmacokinetics (PK) and pharmacodynamics is identification and quantification of the relationships between the parameters and covariates. Lasso has been suggested as a technique for simultaneous estimation and covariate selection. In linear regression, it has been shown that Lasso possesses no oracle properties, which means it asymptotically performs as though the true underlying model was given in advance. Adaptive Lasso (ALasso) with appropriate initial weights is claimed to possess oracle properties; however, it can lead to poor predictive performance when there is multicollinearity between covariates. This simulation study implemented a new version of ALasso, called adjusted ALasso (AALasso), to take into account the ratio of the standard error of the maximum likelihood (ML) estimator to the ML coefficient as the initial weight in ALasso to deal with multicollinearity in non-linear mixed-effect models. The performance of AALasso was compared with that of ALasso and Lasso. PK data was simulated in four set-ups from a one-compartment bolus input model. Covariates were created by sampling from a multivariate standard normal distribution with no, low (0.2), moderate (0.5) or high (0.7) correlation. The true covariates influenced only clearance at different magnitudes. AALasso, ALasso and Lasso were compared in terms of mean absolute prediction error and error of the estimated covariate coefficient. The results show that AALasso performed better in small data sets, even in those in which a high correlation existed between covariates. This makes AALasso a promising method for covariate selection in nonlinear mixed-effect models.

Using biomarker data to adjust estimates of the distribution of usual intakes for misreporting: application to energy intake in the US population.

PubMed

Yanetz, Rivka; Kipnis, Victor; Carroll, Raymond J; Dodd, Kevin W; Subar, Amy F; Schatzkin, Arthur; Freedman, Laurence S

2008-03-01

It is now well-established that individuals misreport their dietary intake. We propose a new method (National Research Council-Biomarker [NRC-B]) for estimating population distributions of usual dietary intake from national survey 24-hour recall data, using additional biomarker data from an external study to adjust for such dietary misreporting. NRC-B is an extension of the NRC method, and is based upon two developed assumptions: the ratio of the mean of true intake to that of reported intake is equal in the survey and external biomarker study; and the ratio of the variance of true intake to that of reported intake is equal in these two studies. NRC-B adjusts the usual intake distribution both for within-person variation and for bias (underreporting) that occur with 24-hour recall reports. Using doubly labeled water ((2)H(2)(18)O) measurements from the Observing Protein and Energy Nutrition study, we applied NRC-B to data on energy intake for adults aged 40 to 69 years from two national surveys, the Continuing Survey of Food Intakes by Individuals and National Health and Nutrition Examination Survey. We compared the results with the NRC and traditional methods that used only the survey data to estimate dietary intake distributions. Estimated distributions from NRC-B and NRC were much narrower and less skewed than from the traditional method. However, unlike NRC, the median of the NRC-B based distribution was higher by 8% to 16% than the traditional method in our examples. The proposed method adjusts for the well-documented problem of underreporting of energy intake.

Assessing the performance of the generalized propensity score for estimating the effect of quantitative or continuous exposures on binary outcomes

PubMed Central

2018-01-01

Propensity score methods are increasingly being used to estimate the effects of treatments and exposures when using observational data. The propensity score was initially developed for use with binary exposures. The generalized propensity score (GPS) is an extension of the propensity score for use with quantitative or continuous exposures (eg, dose or quantity of medication, income, or years of education). We used Monte Carlo simulations to examine the performance of different methods of using the GPS to estimate the effect of continuous exposures on binary outcomes. We examined covariate adjustment using the GPS and weighting using weights based on the inverse of the GPS. We examined both the use of ordinary least squares to estimate the propensity function and the use of the covariate balancing propensity score algorithm. The use of methods based on the GPS was compared with the use of G‐computation. All methods resulted in essentially unbiased estimation of the population dose‐response function. However, GPS‐based weighting tended to result in estimates that displayed greater variability and had higher mean squared error when the magnitude of confounding was strong. Of the methods based on the GPS, covariate adjustment using the GPS tended to result in estimates with lower variability and mean squared error when the magnitude of confounding was strong. We illustrate the application of these methods by estimating the effect of average neighborhood income on the probability of death within 1 year of hospitalization for an acute myocardial infarction. PMID:29508424

Estimation of lactose interference in vaccines and a proposal of methodological adjustment of total protein determination by the lowry method.

PubMed

Kusunoki, Hideki; Okuma, Kazu; Hamaguchi, Isao

2012-01-01

For national regulatory testing in Japan, the Lowry method is used for the determination of total protein content in vaccines. However, many substances are known to interfere with the Lowry method, rendering accurate estimation of protein content difficult. To accurately determine the total protein content in vaccines, it is necessary to identify the major interfering substances and improve the methodology for removing such substances. This study examined the effects of high levels of lactose with low levels of protein in freeze-dried, cell culture-derived Japanese encephalitis vaccine (inactivated). Lactose was selected because it is a reducing sugar that is expected to interfere with the Lowry method. Our results revealed that concentrations of ≥ 0.1 mg/mL lactose interfered with the Lowry assays and resulted in overestimation of the protein content in a lactose concentration-dependent manner. On the other hand, our results demonstrated that it is important for the residual volume to be ≤ 0.05 mL after trichloroacetic acid precipitation in order to avoid the effects of lactose. Thus, the method presented here is useful for accurate protein determination by the Lowry method, even when it is used for determining low levels of protein in vaccines containing interfering substances. In this study, we have reported a methodological adjustment that allows accurate estimation of protein content for national regulatory testing, when the vaccine contains interfering substances.

Effects of LiDAR point density and landscape context on estimates of urban forest biomass

NASA Astrophysics Data System (ADS)

Singh, Kunwar K.; Chen, Gang; McCarter, James B.; Meentemeyer, Ross K.

2015-03-01

Light Detection and Ranging (LiDAR) data is being increasingly used as an effective alternative to conventional optical remote sensing to accurately estimate aboveground forest biomass ranging from individual tree to stand levels. Recent advancements in LiDAR technology have resulted in higher point densities and improved data accuracies accompanied by challenges for procuring and processing voluminous LiDAR data for large-area assessments. Reducing point density lowers data acquisition costs and overcomes computational challenges for large-area forest assessments. However, how does lower point density impact the accuracy of biomass estimation in forests containing a great level of anthropogenic disturbance? We evaluate the effects of LiDAR point density on the biomass estimation of remnant forests in the rapidly urbanizing region of Charlotte, North Carolina, USA. We used multiple linear regression to establish a statistical relationship between field-measured biomass and predictor variables derived from LiDAR data with varying densities. We compared the estimation accuracies between a general Urban Forest type and three Forest Type models (evergreen, deciduous, and mixed) and quantified the degree to which landscape context influenced biomass estimation. The explained biomass variance of the Urban Forest model, using adjusted R2, was consistent across the reduced point densities, with the highest difference of 11.5% between the 100% and 1% point densities. The combined estimates of Forest Type biomass models outperformed the Urban Forest models at the representative point densities (100% and 40%). The Urban Forest biomass model with development density of 125 m radius produced the highest adjusted R2 (0.83 and 0.82 at 100% and 40% LiDAR point densities, respectively) and the lowest RMSE values, highlighting a distance impact of development on biomass estimation. Our evaluation suggests that reducing LiDAR point density is a viable solution to regional

Overcoming bias in estimating the volume-outcome relationship.

PubMed

Tsai, Alexander C; Votruba, Mark; Bridges, John F P; Cebul, Randall D

2006-02-01

To examine the effect of hospital volume on 30-day mortality for patients with congestive heart failure (CHF) using administrative and clinical data in conventional regression and instrumental variables (IV) estimation models. The primary data consisted of longitudinal information on comorbid conditions, vital signs, clinical status, and laboratory test results for 21,555 Medicare-insured patients aged 65 years and older hospitalized for CHF in northeast Ohio in 1991-1997. The patient was the primary unit of analysis. We fit a linear probability model to the data to assess the effects of hospital volume on patient mortality within 30 days of admission. Both administrative and clinical data elements were included for risk adjustment. Linear distances between patients and hospitals were used to construct the instrument, which was then used to assess the endogeneity of hospital volume. When only administrative data elements were included in the risk adjustment model, the estimated volume-outcome effect was statistically significant (p=.029) but small in magnitude. The estimate was markedly attenuated in magnitude and statistical significance when clinical data were added to the model as risk adjusters (p=.39). IV estimation shifted the estimate in a direction consistent with selective referral, but we were unable to reject the consistency of the linear probability estimates. Use of only administrative data for volume-outcomes research may generate spurious findings. The IV analysis further suggests that conventional estimates of the volume-outcome relationship may be contaminated by selective referral effects. Taken together, our results suggest that efforts to concentrate hospital-based CHF care in high-volume hospitals may not reduce mortality among elderly patients.

On-board adaptive model for state of charge estimation of lithium-ion batteries based on Kalman filter with proportional integral-based error adjustment

NASA Astrophysics Data System (ADS)

Wei, Jingwen; Dong, Guangzhong; Chen, Zonghai

2017-10-01

With the rapid development of battery-powered electric vehicles, the lithium-ion battery plays a critical role in the reliability of vehicle system. In order to provide timely management and protection for battery systems, it is necessary to develop a reliable battery model and accurate battery parameters estimation to describe battery dynamic behaviors. Therefore, this paper focuses on an on-board adaptive model for state-of-charge (SOC) estimation of lithium-ion batteries. Firstly, a first-order equivalent circuit battery model is employed to describe battery dynamic characteristics. Then, the recursive least square algorithm and the off-line identification method are used to provide good initial values of model parameters to ensure filter stability and reduce the convergence time. Thirdly, an extended-Kalman-filter (EKF) is applied to on-line estimate battery SOC and model parameters. Considering that the EKF is essentially a first-order Taylor approximation of battery model, which contains inevitable model errors, thus, a proportional integral-based error adjustment technique is employed to improve the performance of EKF method and correct model parameters. Finally, the experimental results on lithium-ion batteries indicate that the proposed EKF with proportional integral-based error adjustment method can provide robust and accurate battery model and on-line parameter estimation.

Can statistic adjustment of OR minimize the potential confounding bias for meta-analysis of case-control study? A secondary data analysis.

PubMed

Liu, Tianyi; Nie, Xiaolu; Wu, Zehao; Zhang, Ying; Feng, Guoshuang; Cai, Siyu; Lv, Yaqi; Peng, Xiaoxia

2017-12-29

Different confounder adjustment strategies were used to estimate odds ratios (ORs) in case-control study, i.e. how many confounders original studies adjusted and what the variables are. This secondary data analysis is aimed to detect whether there are potential biases caused by difference of confounding factor adjustment strategies in case-control study, and whether such bias would impact the summary effect size of meta-analysis. We included all meta-analyses that focused on the association between breast cancer and passive smoking among non-smoking women, as well as each original case-control studies included in these meta-analyses. The relative deviations (RDs) of each original study were calculated to detect how magnitude the adjustment would impact the estimation of ORs, compared with crude ORs. At the same time, a scatter diagram was sketched to describe the distribution of adjusted ORs with different number of adjusted confounders. Substantial inconsistency existed in meta-analysis of case-control studies, which would influence the precision of the summary effect size. First, mixed unadjusted and adjusted ORs were used to combine individual OR in majority of meta-analysis. Second, original studies with different adjustment strategies of confounders were combined, i.e. the number of adjusted confounders and different factors being adjusted in each original study. Third, adjustment did not make the effect size of original studies trend to constringency, which suggested that model fitting might have failed to correct the systematic error caused by confounding. The heterogeneity of confounder adjustment strategies in case-control studies may lead to further bias for summary effect size in meta-analyses, especially for weak or medium associations so that the direction of causal inference would be even reversed. Therefore, further methodological researches are needed, referring to the assessment of confounder adjustment strategies, as well as how to take this kind

ESTIMATING TREATMENT EFFECTS ON HEALTHCARE COSTS UNDER EXOGENEITY: IS THERE A ‘MAGIC BULLET’?

PubMed Central

Polsky, Daniel; Manning, Willard G.

2011-01-01

Methods for estimating average treatment effects, under the assumption of no unmeasured confounders, include regression models; propensity score adjustments using stratification, weighting, or matching; and doubly robust estimators (a combination of both). Researchers continue to debate about the best estimator for outcomes such as health care cost data, as they are usually characterized by an asymmetric distribution and heterogeneous treatment effects,. Challenges in finding the right specifications for regression models are well documented in the literature. Propensity score estimators are proposed as alternatives to overcoming these challenges. Using simulations, we find that in moderate size samples (n= 5000), balancing on propensity scores that are estimated from saturated specifications can balance the covariate means across treatment arms but fails to balance higher-order moments and covariances amongst covariates. Therefore, unlike regression model, even if a formal model for outcomes is not required, propensity score estimators can be inefficient at best and biased at worst for health care cost data. Our simulation study, designed to take a ‘proof by contradiction’ approach, proves that no one estimator can be considered the best under all data generating processes for outcomes such as costs. The inverse-propensity weighted estimator is most likely to be unbiased under alternate data generating processes but is prone to bias under misspecification of the propensity score model and is inefficient compared to an unbiased regression estimator. Our results show that there are no ‘magic bullets’ when it comes to estimating treatment effects in health care costs. Care should be taken before naively applying any one estimator to estimate average treatment effects in these data. We illustrate the performance of alternative methods in a cost dataset on breast cancer treatment. PMID:22199462

Estimating quality-adjusted life-year loss due to noncommunicable diseases in Korean adults through to the year 2040.

PubMed

Ock, Minsu; Han, Jung Won; Lee, Jin Yong; Kim, Seon-Ha; Jo, Min-Woo

2015-01-01

To estimate the loss in quality-adjusted life-years (QALYs) in Korean adults due to 13 noncommunicable diseases (NCDs) in 2010 and predict changes in QALY loss through to the year 2040. Thirteen NCDs (hypertension, diabetes mellitus, hyperlipidemia, stroke, myocardial infarction, angina, arthritis, osteoporosis, asthma, allergic rhinitis, atopic dermatitis, cataract, and depression) were selected from the Korean Community Health Survey 2010. The EuroQol five-dimensional questionnaire index from the Korean Community Health Survey 2010 and the Korean valuation set were used to estimate utility weights according to sex, age, and disease. Morbidity data were also obtained from the Korean Community Health Survey 2010. Mortality data according to disease and life expectancy were retrieved from the Korean Statistical Information Service. To predict future QALY loss, future population projection data from the Korean Statistical Information Service were used as substitutes for 2010 population size. Among the assessed 13 NCDs, the largest total QALY loss was for hypertension (513,113 QALYs; units are omitted hereafter), followed by arthritis (509,317) and stroke (431,049). The largest QALY loss due to mortality was stroke (306,733), whereas the largest QALY loss due to morbidity was arthritis (502,513). By applying the middle estimate of future population, the largest increase in total QALY loss between 2010 and 2040 was for hypertension (840,582), followed by stroke (719,076) and diabetes mellitus (474,607). Hypertension, arthritis, and stroke are important in terms of total QALY loss, which will continuous to increase because of aging. These results could be used to develop cost-effective interventions that reduce the burden of NCDs. Copyright © 2015. Published by Elsevier Inc.

Accounting for individual differences and timing of events: estimating the effect of treatment on criminal convictions in heroin users

PubMed Central

2014-01-01

Background The reduction of crime is an important outcome of opioid maintenance treatment (OMT). Criminal intensity and treatment regimes vary among OMT patients, but this is rarely adjusted for in statistical analyses, which tend to focus on cohort incidence rates and rate ratios. The purpose of this work was to estimate the relationship between treatment and criminal convictions among OMT patients, adjusting for individual covariate information and timing of events, fitting time-to-event regression models of increasing complexity. Methods National criminal records were cross linked with treatment data on 3221 patients starting OMT in Norway 1997–2003. In addition to calculating cohort incidence rates, criminal convictions was modelled as a recurrent event dependent variable, and treatment a time-dependent covariate, in Cox proportional hazards, Aalen’s additive hazards, and semi-parametric additive hazards regression models. Both fixed and dynamic covariates were included. Results During OMT, the number of days with criminal convictions for the cohort as a whole was 61% lower than when not in treatment. OMT was associated with reduced number of days with criminal convictions in all time-to-event regression models, but the hazard ratio (95% CI) was strongly attenuated when adjusting for covariates; from 0.40 (0.35, 0.45) in a univariate model to 0.79 (0.72, 0.87) in a fully adjusted model. The hazard was lower for females and decreasing with older age, while increasing with high numbers of criminal convictions prior to application to OMT (all p < 0.001). The strongest predictors were level of criminal activity prior to entering into OMT, and having a recent criminal conviction (both p < 0.001). The effect of several predictors was significantly time-varying with their effects diminishing over time. Conclusions Analyzing complex observational data regarding to fixed factors only overlooks important temporal information, and naïve cohort level incidence

Accounting for individual differences and timing of events: estimating the effect of treatment on criminal convictions in heroin users.

PubMed

Røislien, Jo; Clausen, Thomas; Gran, Jon Michael; Bukten, Anne

2014-05-17

The reduction of crime is an important outcome of opioid maintenance treatment (OMT). Criminal intensity and treatment regimes vary among OMT patients, but this is rarely adjusted for in statistical analyses, which tend to focus on cohort incidence rates and rate ratios. The purpose of this work was to estimate the relationship between treatment and criminal convictions among OMT patients, adjusting for individual covariate information and timing of events, fitting time-to-event regression models of increasing complexity. National criminal records were cross linked with treatment data on 3221 patients starting OMT in Norway 1997-2003. In addition to calculating cohort incidence rates, criminal convictions was modelled as a recurrent event dependent variable, and treatment a time-dependent covariate, in Cox proportional hazards, Aalen's additive hazards, and semi-parametric additive hazards regression models. Both fixed and dynamic covariates were included. During OMT, the number of days with criminal convictions for the cohort as a whole was 61% lower than when not in treatment. OMT was associated with reduced number of days with criminal convictions in all time-to-event regression models, but the hazard ratio (95% CI) was strongly attenuated when adjusting for covariates; from 0.40 (0.35, 0.45) in a univariate model to 0.79 (0.72, 0.87) in a fully adjusted model. The hazard was lower for females and decreasing with older age, while increasing with high numbers of criminal convictions prior to application to OMT (all p < 0.001). The strongest predictors were level of criminal activity prior to entering into OMT, and having a recent criminal conviction (both p < 0.001). The effect of several predictors was significantly time-varying with their effects diminishing over time. Analyzing complex observational data regarding to fixed factors only overlooks important temporal information, and naïve cohort level incidence rates might result in biased estimates of the

Mexican American Adolescents' Family Caregiving: Selection Effects and Longitudinal Associations with Adjustment

ERIC Educational Resources Information Center

East, Patricia L.; Weisner, Thomas S.

2009-01-01

One hundred ten Mexican American adolescents (12-17 years) who provide infant care for their older sisters were studied to determine the effects of family caregiving responsibilities on adolescents' adjustment. Controlling for prior adjustment and family context factors, providing many hours of caregiving predicted an increase in youths' school…

Unbiased estimation in seamless phase II/III trials with unequal treatment effect variances and hypothesis-driven selection rules.

PubMed

Robertson, David S; Prevost, A Toby; Bowden, Jack

2016-09-30

Seamless phase II/III clinical trials offer an efficient way to select an experimental treatment and perform confirmatory analysis within a single trial. However, combining the data from both stages in the final analysis can induce bias into the estimates of treatment effects. Methods for bias adjustment developed thus far have made restrictive assumptions about the design and selection rules followed. In order to address these shortcomings, we apply recent methodological advances to derive the uniformly minimum variance conditionally unbiased estimator for two-stage seamless phase II/III trials. Our framework allows for the precision of the treatment arm estimates to take arbitrary values, can be utilised for all treatments that are taken forward to phase III and is applicable when the decision to select or drop treatment arms is driven by a multiplicity-adjusted hypothesis testing procedure. © 2016 The Authors. Statistics in Medicine Published by John Wiley & Sons Ltd. © 2016 The Authors. Statistics in Medicine Published by John Wiley & Sons Ltd.

Assessing the performance of the generalized propensity score for estimating the effect of quantitative or continuous exposures on binary outcomes.

PubMed

Austin, Peter C

2018-05-20

Propensity score methods are increasingly being used to estimate the effects of treatments and exposures when using observational data. The propensity score was initially developed for use with binary exposures. The generalized propensity score (GPS) is an extension of the propensity score for use with quantitative or continuous exposures (eg, dose or quantity of medication, income, or years of education). We used Monte Carlo simulations to examine the performance of different methods of using the GPS to estimate the effect of continuous exposures on binary outcomes. We examined covariate adjustment using the GPS and weighting using weights based on the inverse of the GPS. We examined both the use of ordinary least squares to estimate the propensity function and the use of the covariate balancing propensity score algorithm. The use of methods based on the GPS was compared with the use of G-computation. All methods resulted in essentially unbiased estimation of the population dose-response function. However, GPS-based weighting tended to result in estimates that displayed greater variability and had higher mean squared error when the magnitude of confounding was strong. Of the methods based on the GPS, covariate adjustment using the GPS tended to result in estimates with lower variability and mean squared error when the magnitude of confounding was strong. We illustrate the application of these methods by estimating the effect of average neighborhood income on the probability of death within 1 year of hospitalization for an acute myocardial infarction. © 2018 The Authors. Statistics in Medicine published by John Wiley & Sons Ltd.

Sex- and Age-Adjusted Population Analysis of Prevalence Estimates for Hidradenitis Suppurativa in the United States.

PubMed

Garg, Amit; Kirby, Joslyn S; Lavian, Jonathan; Lin, Gloria; Strunk, Andrew

2017-08-01

The true prevalence of hidradenitis suppurativa (HS) is unknown. To establish standardized overall and group-specific prevalence estimates for HS in the United States. This retrospective analysis included a demographically heterogeneous population-based sample of more than 48 million unique patients across all US census regions. As of October 27, 2016, a total of 47 690 patients with HS were identified using electronic health record data. Standardized overall point prevalence for HS and sex-, age-, and race-specific prevalence estimates of HS in the general US population. Of the 47 690 patients with HS (26.2% men and 73.8% women), the overall HS prevalence in the US population sample was 0.10%, or 98 per 100 000 persons (95% CI, 97-99 per 100 000 persons). The adjusted prevalence in women was 137 per 100 000 (95% CI, 136-139 per 100 000), more than twice that of men (58 per 100 000; 95% CI, 57-59 per 100 000; P < .001). The prevalence of HS was highest among patients aged 30 to 39 years (172 per 100 000; 95% CI, 169-275 per 100 000) compared with all other age groups (range, 15-150 per 100 000; P < .001). Adjusted HS prevalences among African American (296 per 100 000; 95% CI, 291-300 per 100 000) and biracial (218 per 100 000; 95% CI, 202-235 per 100 000) patients were more than 3-fold and 2-fold greater, respectively, than that among white patients (95 per 100 000; 95% CI, 94-96 per 100 000; P < .001). Hidradenitis suppurativa is an uncommon, but not rare, disease in the United States that disproportionately affects female patients, young adults, and African American and biracial patients.

A comparison of bootstrap methods and an adjusted bootstrap approach for estimating the prediction error in microarray classification.

PubMed

Jiang, Wenyu; Simon, Richard

2007-12-20

This paper first provides a critical review on some existing methods for estimating the prediction error in classifying microarray data where the number of genes greatly exceeds the number of specimens. Special attention is given to the bootstrap-related methods. When the sample size n is small, we find that all the reviewed methods suffer from either substantial bias or variability. We introduce a repeated leave-one-out bootstrap (RLOOB) method that predicts for each specimen in the sample using bootstrap learning sets of size ln. We then propose an adjusted bootstrap (ABS) method that fits a learning curve to the RLOOB estimates calculated with different bootstrap learning set sizes. The ABS method is robust across the situations we investigate and provides a slightly conservative estimate for the prediction error. Even with small samples, it does not suffer from large upward bias as the leave-one-out bootstrap and the 0.632+ bootstrap, and it does not suffer from large variability as the leave-one-out cross-validation in microarray applications. Copyright (c) 2007 John Wiley & Sons, Ltd.

Effects of Peer Victimization on Psychological and Academic Adjustment in Early Adolescence

ERIC Educational Resources Information Center

Rueger, Sandra Yu; Jenkins, Lyndsay N.

2014-01-01

The purpose of the current study is to investigate the effects of frequency of peer victimization experiences on psychological and academic adjustment during early adolescence, with a focus on testing psychological adjustment as a mediator, as well as differences based on gender and type of victimization. The sample in this short-term longitudinal…

Incorporating the sampling design in weighting adjustments for panel attrition

PubMed Central

Chen, Qixuan; Gelman, Andrew; Tracy, Melissa; Norris, Fran H.; Galea, Sandro

2015-01-01

We review weighting adjustment methods for panel attrition and suggest approaches for incorporating design variables, such as strata, clusters and baseline sample weights. Design information can typically be included in attrition analysis using multilevel models or decision tree methods such as the CHAID algorithm. We use simulation to show that these weighting approaches can effectively reduce bias in the survey estimates that would occur from omitting the effect of design factors on attrition while keeping the resulted weights stable. We provide a step-by-step illustration on creating weighting adjustments for panel attrition in the Galveston Bay Recovery Study, a survey of residents in a community following a disaster, and provide suggestions to analysts in decision making about weighting approaches. PMID:26239405

Burden of typhoid fever in low-income and middle-income countries: a systematic, literature-based update with risk-factor adjustment.

PubMed

Mogasale, Vittal; Maskery, Brian; Ochiai, R Leon; Lee, Jung Seok; Mogasale, Vijayalaxmi V; Ramani, Enusa; Kim, Young Eun; Park, Jin Kyung; Wierzba, Thomas F

2014-10-01

No access to safe water is an important risk factor for typhoid fever, yet risk-level heterogeneity is unaccounted for in previous global burden estimates. Since WHO has recommended risk-based use of typhoid polysaccharide vaccine, we revisited the burden of typhoid fever in low-income and middle-income countries (LMICs) after adjusting for water-related risk. We estimated the typhoid disease burden from studies done in LMICs based on blood-culture-confirmed incidence rates applied to the 2010 population, after correcting for operational issues related to surveillance, limitations of diagnostic tests, and water-related risk. We derived incidence estimates, correction factors, and mortality estimates from systematic literature reviews. We did scenario analyses for risk factors, diagnostic sensitivity, and case fatality rates, accounting for the uncertainty in these estimates and we compared them with previous disease burden estimates. The estimated number of typhoid fever cases in LMICs in 2010 after adjusting for water-related risk was 11·9 million (95% CI 9·9-14·7) cases with 129 000 (75 000-208 000) deaths. By comparison, the estimated risk-unadjusted burden was 20·6 million (17·5-24·2) cases and 223 000 (131 000-344 000) deaths. Scenario analyses indicated that the risk-factor adjustment and updated diagnostic test correction factor derived from systematic literature reviews were the drivers of differences between the current estimate and past estimates. The risk-adjusted typhoid fever burden estimate was more conservative than previous estimates. However, by distinguishing the risk differences, it will allow assessment of the effect at the population level and will facilitate cost-effectiveness calculations for risk-based vaccination strategies for future typhoid conjugate vaccine. Copyright © 2014 Mogasale et al. Open Access article distributed under the terms of CC BY-NC-SA. Published by .. All rights reserved.

Meta-analysis of breast cancer mortality benefit and overdiagnosis adjusted for adherence: improving information on the effects of attending screening mammography

PubMed Central

Jacklyn, Gemma; Glasziou, Paul; Macaskill, Petra; Barratt, Alexandra

2016-01-01

Background: Women require information about the impact of regularly attending screening mammography on breast cancer mortality and overdiagnosis to make informed decisions. To provide this information we aimed to meta-analyse randomised controlled trials adjusted for adherence to the trial protocol. Methods: Nine screening mammography trials used in the Independent UK Breast Screening Report were selected. Extending an existing approach to adjust intention-to-treat (ITT) estimates for less than 100% adherence rates, we conducted a random-effects meta-analysis. This produced a combined deattenuated prevented fraction and a combined deattenuated percentage risk of overdiagnosis. Results: In women aged 39–75 years invited to screen, the prevented fraction of breast cancer mortality at 13-year follow-up was 0.22 (95% CI 0.15–0.28) and it increased to 0.30 (95% CI 0.18–0.42) with deattenuation. In women aged 40–69 years invited to screen, the ITT percentage risk of overdiagnosis during the screening period was 19.0% (95% CI 15.2–22.7%), deattenuation increased this to 29.7% (95% CI 17.8–41.5%). Conclusions: Adjustment for nonadherence increased the size of the mortality benefit and risk of overdiagnosis by up to 50%. These estimates are more appropriate when developing quantitative information to support individual decisions about attending screening mammography. PMID:27124337

On the Estimation of the Cost-Effectiveness Threshold: Why, What, How?

PubMed

Vallejo-Torres, Laura; García-Lorenzo, Borja; Castilla, Iván; Valcárcel-Nazco, Cristina; García-Pérez, Lidia; Linertová, Renata; Polentinos-Castro, Elena; Serrano-Aguilar, Pedro

2016-01-01

Many health care systems claim to incorporate the cost-effectiveness criterion in their investment decisions. Information on the system's willingness to pay per effectiveness unit, normally measured as quality-adjusted life-years (QALYs), however, is not available in most countries. This is partly because of the controversy that remains around the use of a cost-effectiveness threshold, about what the threshold ought to represent, and about the appropriate methodology to arrive at a threshold value. The aim of this article was to identify and critically appraise the conceptual perspectives and methodologies used to date to estimate the cost-effectiveness threshold. We provided an in-depth discussion of different conceptual views and undertook a systematic review of empirical analyses. Identified studies were categorized into the two main conceptual perspectives that argue that the threshold should reflect 1) the value that society places on a QALY and 2) the opportunity cost of investment to the system given budget constraints. These studies showed different underpinning assumptions, strengths, and limitations, which are highlighted and discussed. Furthermore, this review allowed us to compare the cost-effectiveness threshold estimates derived from different types of studies. We found that thresholds based on society's valuation of a QALY are generally larger than thresholds resulting from estimating the opportunity cost to the health care system. This implies that some interventions with positive social net benefits, as informed by individuals' preferences, might not be an appropriate use of resources under fixed budget constraints. Copyright © 2016 International Society for Pharmacoeconomics and Outcomes Research (ISPOR). Published by Elsevier Inc. All rights reserved.

Assessing and adjusting for differences between HIV prevalence estimates derived from national population-based surveys and antenatal care surveillance, with applications for Spectrum 2013

PubMed Central

Marsh, Kimberly; Mahy, Mary; Salomon, Joshua A.; Hogan, Daniel R.

2014-01-01

Objective(s): To assess differences between HIV prevalence estimates derived from national population surveys and antenatal care (ANC) surveillance sites and to improve the calibration of ANC-derived estimates in Spectrum 2013 to more appropriately account for differences between these data. Design: Retrospective analysis of national population survey and ANC surveillance data from 25 countries with generalized epidemics in sub-Saharan Africa and 8 countries with concentrated epidemics. Methods: Adult national population survey and ANC surveillance HIV prevalence estimates were compared for all available national population survey data points for the years 1999–2012. For sub-Saharan Africa, a mixed-effects linear regression model determined whether the relationship between national population and ANC estimates was constant across surveys. A new calibration method was developed to incorporate national population survey data directly into the likelihood for HIV prevalence in countries with generalized epidemics. Results were used to develop default rules for adjusting ANC data for countries with no national population surveys. Results: ANC surveillance data typically overestimate population prevalence, although a wide variation, particularly in rural areas, is observed across countries and survey years. The new calibration method yields similar point estimates to previous approaches, but leads to an average 44% increase in the width of 95% uncertainty intervals. Conclusion: Important biases remain in ANC surveillance data for HIV prevalence. The new approach to model-fitting in Spectrum 2013 more appropriately accounts for this bias when producing national estimates in countries with generalized epidemics. In countries with concentrated epidemics, local sex ratios should be used to calibrate ANC surveillance estimates. PMID:25203158

The stress-buffering effects of hope on changes in adjustment to caregiving in multiple sclerosis.

PubMed

Madan, Sindia; Pakenham, Kenneth I

2015-09-01

This study examined the direct and stress-buffering effects of global hope and its components (agency and pathways) on changes in adjustment to multiple sclerosis caregiving over 12 months. A total of 140 carers and their care-recipients completed questionnaires at Time 1 and 12 months later, Time 2. Focal predictors were stress, hope, agency and pathways, and the adjustment outcomes were anxiety, depression, positive affect, positive states of mind and life satisfaction. Results showed that as predicted, greater hope was associated with better adjustment after controlling for the effects of initial adjustment and caregiving and care-recipient illness variables. No stress-buffering effects of hope emerged. Regarding hope components, only the agency dimension emerged as a significant predictor of adjustment. Findings highlight hope as an important protective resource for coping with multiple sclerosis caregiving and underscore the role of agency thinking in this process. © The Author(s) 2013.

Dynamic adjustment in agricultural practices to economic incentives aiming to decrease fertilizer application.

PubMed

Sun, Shanxia; Delgado, Michael S; Sesmero, Juan P

2016-07-15

Input- and output-based economic policies designed to reduce water pollution from fertilizer runoff by adjusting management practices are theoretically justified and well-understood. Yet, in practice, adjustment in fertilizer application or land allocation may be sluggish. We provide practical guidance for policymakers regarding the relative magnitude and speed of adjustment of input- and output-based policies. Through a dynamic dual model of corn production that takes fertilizer as one of several production inputs, we measure the short- and long-term effects of policies that affect the relative prices of inputs and outputs through the short- and long-term price elasticities of fertilizer application, and also the total time required for different policies to affect fertilizer application through the adjustment rates of capital and land. These estimates allow us to compare input- and output-based policies based on their relative cost-effectiveness. Using data from Indiana and Illinois, we find that input-based policies are more cost-effective than their output-based counterparts in achieving a target reduction in fertilizer application. We show that input- and output-based policies yield adjustment in fertilizer application at the same speed, and that most of the adjustment takes place in the short-term. Copyright © 2016 Elsevier Ltd. All rights reserved.

Refractive accuracy with light-adjustable intraocular lenses.

PubMed

Villegas, Eloy A; Alcon, Encarna; Rubio, Elena; Marín, José M; Artal, Pablo

2014-07-01

To evaluate efficacy, predictability, and stability of refractive treatments using light-adjustable intraocular lenses (IOLs). University Hospital Virgen de la Arrixaca, Murcia, Spain. Prospective nonrandomized clinical trial. Eyes with a light-adjustable IOL (LAL) were treated with spatial intensity profiles to correct refractive errors. The effective changes in refraction in the light-adjustable IOL after every treatment were estimated by subtracting those in the whole eye and the cornea, which were measured with a Hartmann-Shack sensor and a corneal topographer, respectively. The refractive changes in the whole eye and light-adjustable IOL, manifest refraction, and visual acuity were obtained after every light treatment and at the 3-, 6-, and 12-month follow-ups. The study enrolled 53 eyes (49 patients). Each tested light spatial pattern (5 spherical; 3 astigmatic) produced a different refractive change (P<.01). The combination of 2 light adjustments induced a maximum change in spherical power of the light-adjustable IOL of between -1.98 diopters (D) and +2.30 D and in astigmatism of up to -2.68 D with axis errors below 9 degrees. Intersubject variability (standard deviation) ranged between 0.10 D and 0.40 D. The 2 required lock-in procedures induced a small myopic shift (range +0.01 to +0.57 D) that depended on previous adjustments. Light-adjustable IOL implantation achieved accurate refractive outcomes (around emmetropia) with good uncorrected distance visual acuity, which remained stable over time. Further refinements in nomograms and in the treatment's protocol would improve the predictability of refractive and visual outcomes with these IOLs. No author has a financial or proprietary interest in any material or method mentioned. Copyright © 2014 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Effect of distance-related heterogeneity on population size estimates from point counts

USGS Publications Warehouse

Efford, Murray G.; Dawson, Deanna K.

2009-01-01

Point counts are used widely to index bird populations. Variation in the proportion of birds counted is a known source of error, and for robust inference it has been advocated that counts be converted to estimates of absolute population size. We used simulation to assess nine methods for the conduct and analysis of point counts when the data included distance-related heterogeneity of individual detection probability. Distance from the observer is a ubiquitous source of heterogeneity, because nearby birds are more easily detected than distant ones. Several recent methods (dependent double-observer, time of first detection, time of detection, independent multiple-observer, and repeated counts) do not account for distance-related heterogeneity, at least in their simpler forms. We assessed bias in estimates of population size by simulating counts with fixed radius w over four time intervals (occasions). Detection probability per occasion was modeled as a half-normal function of distance with scale parameter sigma and intercept g(0) = 1.0. Bias varied with sigma/w; values of sigma inferred from published studies were often 50% for a 100-m fixed-radius count. More critically, the bias of adjusted counts sometimes varied more than that of unadjusted counts, and inference from adjusted counts would be less robust. The problem was not solved by using mixture models or including distance as a covariate. Conventional distance sampling performed well in simulations, but its assumptions are difficult to meet in the field. We conclude that no existing method allows effective estimation of population size from point counts.

Estimating the cost-effectiveness of 54 weeks of infliximab for rheumatoid arthritis.

PubMed

Wong, John B; Singh, Gurkirpal; Kavanaugh, Arthur

2002-10-01

To estimate the cost-effectiveness of infliximab plus methotrexate for active, refractory rheumatoid arthritis. We projected the 54-week results from a randomized controlled trial of infliximab into lifetime economic and clinical outcomes using a Markov computer simulation model. Direct and indirect costs, quality of life, and disability estimates were based on trial results; Arthritis, Rheumatism, and Aging Medical Information System (ARAMIS) database outcomes; and published data. Results were discounted using the standard 3% rate. Because most well-accepted medical therapies have cost-effectiveness ratios below $50,000 to $100,000 per quality-adjusted life-year (QALY) gained, results below this range were considered to be "cost-effective." At 3 mg/kg, each infliximab infusion would cost $1393. When compared with methotrexate alone, 54 weeks of infliximab plus methotrexate decreased the likelihood of having advanced disability from 23% to 11% at the end of 54 weeks, which projected to a lifetime marginal cost-effectiveness ratio of $30,500 per discounted QALY gained, considering only direct medical costs. When applying a societal perspective and including indirect or productivity costs, the marginal cost-effectiveness ratio for infliximab was $9100 per discounted QALY gained. The results remained relatively unchanged with variation of model estimates over a broad range of values. Infliximab plus methotrexate for 54 weeks for rheumatoid arthritis should be cost-effective with its clinical benefit providing good value for the drug cost, especially when including productivity losses. Although infliximab beyond 54 weeks will likely be cost-effective, the economic and clinical benefit remains uncertain and will depend on long-term results of clinical trials.

Risk-adjusted econometric model to estimate postoperative costs: an additional instrument for monitoring performance after major lung resection.

PubMed

Brunelli, Alessandro; Salati, Michele; Refai, Majed; Xiumé, Francesco; Rocco, Gaetano; Sabbatini, Armando

2007-09-01

The objectives of this study were to develop a risk-adjusted model to estimate individual postoperative costs after major lung resection and to use it for internal economic audit. Variable and fixed hospital costs were collected for 679 consecutive patients who underwent major lung resection from January 2000 through October 2006 at our unit. Several preoperative variables were used to develop a risk-adjusted econometric model from all patients operated on during the period 2000 through 2003 by a stepwise multiple regression analysis (validated by bootstrap). The model was then used to estimate the postoperative costs in the patients operated on during the 3 subsequent periods (years 2004, 2005, and 2006). Observed and predicted costs were then compared within each period by the Wilcoxon signed rank test. Multiple regression and bootstrap analysis yielded the following model predicting postoperative cost: 11,078 + 1340.3X (age > 70 years) + 1927.8X cardiac comorbidity - 95X ppoFEV1%. No differences between predicted and observed costs were noted in the first 2 periods analyzed (year 2004, $6188.40 vs $6241.40, P = .3; year 2005, $6308.60 vs $6483.60, P = .4), whereas in the most recent period (2006) observed costs were significantly lower than the predicted ones ($3457.30 vs $6162.70, P < .0001). Greater precision in predicting outcome and costs after therapy may assist clinicians in the optimization of clinical pathways and allocation of resources. Our economic model may be used as a methodologic template for economic audit in our specialty and complement more traditional outcome measures in the assessment of performance.

Evaluating the effects of variation in clinical practice: a risk adjusted cost-effectiveness (RAC-E) analysis of acute stroke services.

PubMed

Pham, Clarabelle; Caffrey, Orla; Ben-Tovim, David; Hakendorf, Paul; Crotty, Maria; Karnon, Jonathan

2012-08-21

Methods for the cost-effectiveness analysis of health technologies are now well established, but such methods may also have a useful role in the context of evaluating the effects of variation in applied clinical practice. This study illustrates a general methodology for the comparative analysis of applied clinical practice at alternative institutions--risk adjusted cost-effectiveness (RAC-E) analysis--with an application that compares acute hospital services for stroke patients admitted to the main public hospitals in South Australia. Using linked, routinely collected data on all South Australian hospital separations from July 2001 to June 2008, an analysis of the RAC-E of services provided at four metropolitan hospitals was undertaken using a decision analytic framework. Observed (plus extrapolated) and expected lifetime costs and survival were compared across patient populations, from which the relative cost-effectiveness of services provided at the different hospitals was estimated. Unadjusted results showed that at one hospital patients incurred fewer costs and gained more life years than at the other hospitals (i.e. it was the dominant hospital). After risk adjustment, the cost minimizing hospital incurred the lowest costs, but with fewer life-years gained than one other hospital. The mean incremental cost per life-year gained of services provided at the most effective hospital was under $20,000, with an associated 65% probability of being cost-effective at a $50,000 per life year monetary threshold. RAC-E analyses can be used to identify important variation in the costs and outcomes associated with clinical practice at alternative institutions. Such data provides an impetus for further investigation to identify specific areas of variation, which may then inform the dissemination of best practice service delivery and organisation.

Estimates of utility weights in hemophilia: implications for cost-utility analysis of clotting factor prophylaxis

PubMed Central

Grosse, Scott D; Chaugule, Shraddha S; Hay, Joel W

2015-01-01

Estimates of preference-weighted health outcomes or health state utilities are needed to assess improvements in health in terms of quality-adjusted life-years. Gains in quality-adjusted life-years are used to assess the cost–effectiveness of prophylactic use of clotting factor compared with on-demand treatment among people with hemophilia, a congenital bleeding disorder. Published estimates of health utilities for people with hemophilia vary, contributing to uncertainty in the estimates of cost–effectiveness of prophylaxis. Challenges in estimating utility weights for the purpose of evaluating hemophilia treatment include selection bias in observational data, difficulty in adjusting for predictors of health-related quality of life and lack of preference-based data comparing adults with lifetime or primary prophylaxis versus no prophylaxis living within the same country and healthcare system. PMID:25585817

Motivating drivers to correctly adjust head restraints: assessing effectiveness of three different interventions.

PubMed

Fockler, S K; Vavrik, J; Kristiansen, L

1998-11-01

Three types of driver educational strategies were tested to determine the most effective approach for motivating drivers to adjust their head restraints to the correct vertical position: (1) a human interactive personal contact with a member of an ICBC-trained head restraint adjustment team, (2) a passive video presentation of the consequences of correct and incorrect head restraint adjustment, and (3) an interactive three-dimensional kinetic model showing the consequences of correct and incorrect head restraint adjustment. An experimental pretest-posttest control group design was used. A different educational treatment was used in each of three lanes of a vehicle emissions testing facility, with a fourth lane with no intervention serving as a control group. Observational and self-reported data were obtained from a total of 1,974 vehicles entering and exiting the facility. The human intervention led to significantly more drivers actually adjusting their head restraints immediately after the intervention than the passive video or interactive kinetic model approaches, which were both no different from the control group. The human intervention was recommended as the most effective and was implemented successfully on a limited basis during 3 months of 1995 and again during 3 months of 1996.

Comparison of Two Methods for Estimating Adjustable One-Point Cane Length in Community-Dwelling Older Adults.

PubMed

Camara, Camila Thais Pinto; de Freitas, Sandra Maria Sbeghen Ferreira; de Lima, Waléria Paixão; Lima, Camila Astolphi; Amorim, César Ferreira; Perracini, Monica Rodrigues

2017-01-01

Our aim is to estimate inter-observer reliability, test-retest reliability, anthropometric and biomechanical adequacy and minimal detectable change when measuring the length of single-point adjustable canes in community-dwelling older adults. There are 112 participants in the study. They are men and women, aged 60 years and over, who were attending an outpatient community health centre. An exploratory study design was used. Participants underwent two assessments within the same day by two independent observers and by the same observer at an interval of 15-45 days. Two measures were used to establish the length of a single-point adjustable cane: the distance from the distal wrist crease to the floor (WF) and the distance from the top of the greater trochanter of the femur to the floor (TF). Each individual was fitted according to these two measures, and elbow flexion angle was measured. Inter-observer reliability and the test-retest reliability were high in both TF (ICC 3.1  = 0.918 and ICC 2.1  = 0.935) and WF measures (ICC 3.1  = 0.967 and ICC 2.1  = 0.960). Only 1% of the individuals kept an elbow flexion angle within the standard recommendation of 30° ± 10° when the cane length was determined by the TF measure, and 30% of the participants when the cane was determined by the WF measure. The minimal detectable cane length change was 2.2 cm. Our results suggest that, even though both measures are reliable, cane length determined by WF distance is more appropriate to keep the elbow flexion angle within the standard recommendation. The minimal detectable change corresponds to approximately a hole in the cane adjustment. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

Improving causal inference with a doubly robust estimator that combines propensity score stratification and weighting.

PubMed

Linden, Ariel

2017-08-01

When a randomized controlled trial is not feasible, health researchers typically use observational data and rely on statistical methods to adjust for confounding when estimating treatment effects. These methods generally fall into 3 categories: (1) estimators based on a model for the outcome using conventional regression adjustment; (2) weighted estimators based on the propensity score (ie, a model for the treatment assignment); and (3) "doubly robust" (DR) estimators that model both the outcome and propensity score within the same framework. In this paper, we introduce a new DR estimator that utilizes marginal mean weighting through stratification (MMWS) as the basis for weighted adjustment. This estimator may prove more accurate than treatment effect estimators because MMWS has been shown to be more accurate than other models when the propensity score is misspecified. We therefore compare the performance of this new estimator to other commonly used treatment effects estimators. Monte Carlo simulation is used to compare the DR-MMWS estimator to regression adjustment, 2 weighted estimators based on the propensity score and 2 other DR methods. To assess performance under varied conditions, we vary the level of misspecification of the propensity score model as well as misspecify the outcome model. Overall, DR estimators generally outperform methods that model one or the other components (eg, propensity score or outcome). The DR-MMWS estimator outperforms all other estimators when both the propensity score and outcome models are misspecified and performs equally as well as other DR estimators when only the propensity score is misspecified. Health researchers should consider using DR-MMWS as the principal evaluation strategy in observational studies, as this estimator appears to outperform other estimators in its class. © 2017 John Wiley & Sons, Ltd.

Phantom-derived estimation of effective dose equivalent from X rays with and without a lead apron.

PubMed

Mateya, C F; Claycamp, H G

1997-06-01

Organ dose equivalents were measured in a humanoid phantom in order to estimate effective dose equivalent (H(E)) and effective dose (E) from low-energy x rays and in the presence or absence of a protective lead apron. Plane-parallel irradiation conditions were approximated using direct x-ray beams of 76 and 104 kVp and resulting dosimetry data was adjusted to model exposures conditions in fluoroscopy settings. Values of H(E) and E estimated under-shielded conditions were compared to the results of several recent studies that used combinations of measured and calculated dosimetry to model exposures to radiologists. While the estimates of H(E) and E without the lead apron were within 0.2 to 20% of expected values, estimates based on personal monitors worn at the (phantom) waist (underneath the apron) underestimated either H(E) or E while monitors placed at the neck (above the apron) significantly overestimated both quantities. Also, the experimentally determined H(E) and E were 1.4 to 3.3 times greater than might be estimated using recently reported "two-monitor" algorithms for the estimation of effective dose quantities. The results suggest that accurate estimation of either H(E) or E from personal monitors under conditions of partial body exposures remains problematic and is likely to require the use of multiple monitors.

Cost-Effective Adjustments to Nursing Home Staffing to Improve Quality.

PubMed

Bowblis, John R; Roberts, Amy Restorick

2018-06-01

Health care providers face fixed reimbursement rates from government sources and need to carefully adjust staffing to achieve the highest quality within a given cost structure. With data from the Certification and Survey Provider Enhanced Reports (1999-2015), this study holistically examined how staffing levels affect two publicly reported measures of quality in the nursing home industry, the number of deficiency citations and the deficiency score. While higher staffing consistently yielded better quality, the largest quality improvements resulted from increasing administrative registered nurses and social service staffing. After adjusting for wages, the most cost-effective investment for improving overall deficiency outcomes was increasing social services. Deficiencies related to quality of care were improved most by increasing administrative nursing and social service staff. Quality of life deficiencies were improved most by increasing social service and activities staff. Approaches to improve quality through staffing adjustments should target specific types of staff to maximize return on investment.

Parental smoking and childhood obesity: higher effect estimates for maternal smoking in pregnancy compared with paternal smoking--a meta-analysis.

PubMed

Riedel, Christina; Schönberger, Katharina; Yang, Seungmi; Koshy, Gibby; Chen, Yang-Ching; Gopinath, Bamini; Ziebarth, Stephanie; von Kries, Rüdiger

2014-10-01

Some studies reported similar effect estimates for the impact of maternal smoking in pregnancy and paternal smoking on childhood obesity, whereas others suggested higher effects for maternal smoking. We performed a meta-analysis to compare the effect of in utero exposure to maternal smoking and that of paternal or household smoking exposure in utero or after birth with mutual adjustment. Meta-analysis of observational studies identified in MEDLINE, EMBASE and Web of Knowledge published in 1900-2013. Study inclusion criterion was assessment of the association of maternal smoking during pregnancy and paternal or household smoking (anyone living in the household who smokes) at any time with childhood overweight and obesity. The analyses were based on all studies with mutually adjusted effect estimates for maternal and paternal/household smoking applying a random-effects model. Data for 109,838 mother/child pairs were reported in 12 studies. The pooled odds ratios (ORs) for overweight 1.33 [95% confidence interval (CI) 1.23;1.44] (n=6, I2=0.00%) and obesity 1.60 (95% CI 1.37;1.88) (n=4, I2=32.47%) for maternal smoking during pregnancy were higher than for paternal smoking: 1.07 (95% CI 1.00;1.16) (n=6, I2=41.34%) and 1.23 (95% CI 1.10;1.38) (n=4, I2=14.61%), respectively. Similar estimates with widely overlapping confidence limits were found for maternal smoking during pregnancy and childhood overweight and obesity: 1.35 (95% CI 1.20;1.51) (n=3, I2=0.00%) and 1.28 (95% CI 1.07;1.54) (n=3, I2=0.00%) compared with household smoking 1.22 (95% CI 1.06;1.39) (n=3, I2=72.14%) and 1.31 (95% CI 1.15;1.50)] (n=3, I2=0.00%). Higher effect estimates for maternal smoking in pregnancy compared with paternal smoking in mutually adjusted models may suggest a direct intrauterine effect. © The Author 2014; all rights reserved. Published by Oxford University Press on behalf of the International Epidemiological Association.

A risk-adjusted financial model to estimate the cost of a video-assisted thoracoscopic surgery lobectomy programme.

PubMed

Brunelli, Alessandro; Tentzeris, Vasileios; Sandri, Alberto; McKenna, Alexandra; Liew, Shan Liung; Milton, Richard; Chaudhuri, Nilanjan; Kefaloyannis, Emmanuel; Papagiannopoulos, Kostas

2016-05-01

To develop a clinically risk-adjusted financial model to estimate the cost associated with a video-assisted thoracoscopic surgery (VATS) lobectomy programme. Prospectively collected data of 236 VATS lobectomy patients (August 2012-December 2013) were analysed retrospectively. Fixed and variable intraoperative and postoperative costs were retrieved from the Hospital Accounting Department. Baseline and surgical variables were tested for a possible association with total cost using a multivariable linear regression and bootstrap analyses. Costs were calculated in GBP and expressed in Euros (EUR:GBP exchange rate 1.4). The average total cost of a VATS lobectomy was €11 368 (range €6992-€62 535). Average intraoperative (including surgical and anaesthetic time, overhead, disposable materials) and postoperative costs [including ward stay, high dependency unit (HDU) or intensive care unit (ICU) and variable costs associated with management of complications] were €8226 (range €5656-€13 296) and €3029 (range €529-€51 970), respectively. The following variables remained reliably associated with total costs after linear regression analysis and bootstrap: carbon monoxide lung diffusion capacity (DLCO) <60% predicted value (P = 0.02, bootstrap 63%) and chronic obstructive pulmonary disease (COPD; P = 0.035, bootstrap 57%). The following model was developed to estimate the total costs: 10 523 + 1894 × COPD + 2376 × DLCO < 60%. The comparison between predicted and observed costs was repeated in 1000 bootstrapped samples to verify the stability of the model. The two values were not different (P > 0.05) in 86% of the samples. A hypothetical patient with COPD and DLCO less than 60% would cost €4270 more than a patient without COPD and with higher DLCO values (€14 793 vs €10 523). Risk-adjusting financial data can help estimate the total cost associated with VATS lobectomy based on clinical factors. This model can be used to audit the internal financial

Secukinumab Versus Adalimumab for Psoriatic Arthritis: Comparative Effectiveness up to 48 Weeks Using a Matching-Adjusted Indirect Comparison.

PubMed

Nash, Peter; McInnes, Iain B; Mease, Philip J; Thom, Howard; Hunger, Matthias; Karabis, Andreas; Gandhi, Kunal; Mpofu, Shephard; Jugl, Steffen M

2018-06-01

Secukinumab and adalimumab are approved for adults with active psoriatic arthritis (PsA). In the absence of direct randomized controlled trial (RCT) data, matching-adjusted indirect comparison can estimate the comparative effectiveness in anti-tumor necrosis factor (TNF)-naïve populations. Individual patient data from the FUTURE 2 RCT (secukinumab vs. placebo; N = 299) were adjusted to match baseline characteristics of the ADEPT RCT (adalimumab vs. placebo; N = 313). Logistic regression determined adjustment weights for age, body weight, sex, race, methotrexate use, psoriasis affecting ≥ 3% of body surface area, Psoriasis Area and Severity Index score, Health Assessment Questionnaire Disability Index score, presence of dactylitis and enthesitis, and previous anti-TNF therapy. Recalculated secukinumab outcomes were compared with adalimumab outcomes at weeks 12 (placebo-adjusted), 16, 24, and 48 (nonplacebo-adjusted). After matching, the effective sample size for FUTURE 2 was 101. Week 12 American College of Rheumatology (ACR) response rates were not significantly different between secukinumab and adalimumab. Week 16 ACR 20 and 50 response rates were higher for secukinumab 150 mg than for adalimumab (P = 0.017, P = 0.033), as was ACR 50 for secukinumab 300 mg (P = 0.030). Week 24 ACR 20 and 50 were higher for secukinumab 150 mg than for adalimumab (P = 0.001, P = 0.019), as was ACR 20 for secukinumab 300 mg (P = 0.048). Week 48 ACR 20 was higher for secukinumab 150 and 300 mg than for adalimumab (P = 0.002, P = 0.027), as was ACR 50 for secukinumab 300 mg (P = 0.032). In our analysis, patients with PsA receiving secukinumab were more likely to achieve higher ACR responses through 1 year (weeks 16-48) than those treated with adalimumab. Although informative, these observations rely on a subgroup of patients from FUTURE 2 and thus should be considered interim until the ongoing head-to-head RCT EXCEED can

Adjustment to time of use pricing: Persistence of habits or change

NASA Astrophysics Data System (ADS)

Rebello, Derrick Michael

1999-11-01

Generally the dynamics related to residential electricity consumption under TOU rates have not been analyzed completely. A habit persistence model is proposed to account for the dynamics that may be present as a result of recurring habits or lack of information about the effects of shifting load across TOU periods. In addition, the presence of attrition bias necessitated a two-step estimation approach. The decision to remain in the program modeled in the first-step, while demand for electricity was estimated in the second-step. Results show that own-price effects and habit persistence have the most significant effect the model. The habit effects, which while small in absolute terms, are significant. Elasticity estimates show that electricity consumption is inelastic during all periods of the day. Estimates of the long-run elasticities were nearly identical to short-run estimates, showing little or no adjustment across time. Cross-price elasticities indicate a willingness to substitute consumption across periods implying that TOU goods are weak substitutes. The most significant substitution occurs during the period of 5:00 PM to 9:00 PM, when most individuals are likely to be home and active.

Empirical evidence for resource-rational anchoring and adjustment.

PubMed

Lieder, Falk; Griffiths, Thomas L; M Huys, Quentin J; Goodman, Noah D

2018-04-01

People's estimates of numerical quantities are systematically biased towards their initial guess. This anchoring bias is usually interpreted as sign of human irrationality, but it has recently been suggested that the anchoring bias instead results from people's rational use of their finite time and limited cognitive resources. If this were true, then adjustment should decrease with the relative cost of time. To test this hypothesis, we designed a new numerical estimation paradigm that controls people's knowledge and varies the cost of time and error independently while allowing people to invest as much or as little time and effort into refining their estimate as they wish. Two experiments confirmed the prediction that adjustment decreases with time cost but increases with error cost regardless of whether the anchor was self-generated or provided. These results support the hypothesis that people rationally adapt their number of adjustments to achieve a near-optimal speed-accuracy tradeoff. This suggests that the anchoring bias might be a signature of the rational use of finite time and limited cognitive resources rather than a sign of human irrationality.

Cost Effectiveness of Childhood Cochlear Implantation and Deaf Education in Nicaragua: A Disability Adjusted Life Year Model.

PubMed

Saunders, James E; Barrs, David M; Gong, Wenfeng; Wilson, Blake S; Mojica, Karen; Tucci, Debara L

2015-09-01

Cochlear implantation (CI) is a common intervention for severe-to-profound hearing loss in high-income countries, but is not commonly available to children in low resource environments. Owing in part to the device costs, CI has been assumed to be less economical than deaf education for low resource countries. The purpose of this study is to compare the cost effectiveness of the two interventions for children with severe-to-profound sensorineural hearing loss (SNHL) in a model using disability adjusted life years (DALYs). Cost estimates were derived from published data, expert opinion, and known costs of services in Nicaragua. Individual costs and lifetime DALY estimates with a 3% discounting rate were applied to both two interventions. Sensitivity analysis was implemented to evaluate the effect on the discounted cost of five key components: implant cost, audiology salary, speech therapy salary, number of children implanted per year, and device failure probability. The costs per DALY averted are $5,898 and $5,529 for CI and deaf education, respectively. Using standards set by the WHO, both interventions are cost effective. Sensitivity analysis shows that when all costs set to maximum estimates, CI is still cost effective. Using a conservative DALY analysis, both CI and deaf education are cost-effective treatment alternatives for severe-to-profound SNHL. CI intervention costs are not only influenced by the initial surgery and device costs but also by rehabilitation costs and the lifetime maintenance, device replacement, and battery costs. The major CI cost differences in this low resource setting were increased initial training and infrastructure costs, but lower medical personnel and surgery costs.

Appraisal and coping styles account for the effects of temperament on preadolescent adjustment

PubMed Central

Thompson, Stephanie F.; Zalewski, Maureen; Lengua, Liliana J.

2014-01-01

Temperament, appraisal, and coping are known to underlie emotion regulation, yet less is known about how these processes relate to each other across time. We examined temperamental fear, frustration, effortful control, and impulsivity, positive and threat appraisals, and active and avoidant coping as processes underpinning the emotion regulation of pre-adolescent children managing stressful events. Appraisal and coping styles were tested as mediators of the longitudinal effects of temperamental emotionality and self-regulation on adjustment using a community sample (N=316) of preadolescent children (8–12 years at T1) studied across one year. High threat appraisals were concurrently related to high fear and impulsivity, whereas effortful control predicted relative decreases in threat appraisal. High fear was concurrently related to high positive appraisal, and impulsivity predicted increases in positive appraisal. Fear was concurrently related to greater avoidant coping, and impulsivity predicted increases in avoidance. Frustration predicted decreases in active coping. These findings suggest temperament, or dispositional aspects of reactivity and regulation, relates to concurrent appraisal and coping processes and additionally predicts change in these processes. Significant indirect effects indicated that appraisal and coping mediated the effects of temperament on adjustment. Threat appraisal mediated the effects of fear and effortful control on internalizing and externalizing problems, and avoidant coping mediated the effect of impulsivity on internalizing problems. These mediated effects suggest that one pathway through which temperament influences adjustment is pre-adolescents’ appraisal and coping. Findings highlight temperament, appraisal and coping as emotion regulation processes relevant to children’s adjustment in response to stress. PMID:25821237

Weather adjustment using seemingly unrelated regression

DOE Office of Scientific and Technical Information (OSTI.GOV)

Noll, T.A.

1995-05-01

Seemingly unrelated regression (SUR) is a system estimation technique that accounts for time-contemporaneous correlation between individual equations within a system of equations. SUR is suited to weather adjustment estimations when the estimation is: (1) composed of a system of equations and (2) the system of equations represents either different weather stations, different sales sectors or a combination of different weather stations and different sales sectors. SUR utilizes the cross-equation error values to develop more accurate estimates of the system coefficients than are obtained using ordinary least-squares (OLS) estimation. SUR estimates can be generated using a variety of statistical software packagesmore » including MicroTSP and SAS.« less

Effects of enterostomal nurse telephone follow-up on postoperative adjustment of discharged colostomy patients.

PubMed

Zhang, Jun-e; Wong, Frances Kam Yuet; You, Li-ming; Zheng, Mei-chun; Li, Qiong; Zhang, Bing-yan; Huang, Man-rong; Ye, Xin-Mei; Liang, Ming-juan; Liu, Jin-ling

2013-01-01

People with a new colostomy encounter many difficulties as they struggle to adjust to their ostomies. Nurse telephone follow-up is a convenient way to ensure continuity of care. There is a paucity of studies testing if nurse telephone follow-up can enhance adjustment of postdischarged colostomy patients. The purpose of this study was to evaluate the effect of enterostomal nurse telephone follow-up on the adjustment levels of discharged colostomy patients. This was a randomized controlled trial. Participants (n = 103) who had undergone colostomy operations in China were recruited and randomly assigned to the study or control group. Both the study and control groups received routine discharge care, whereas the study group received 2-3 nurse telephone calls in the follow-up period. The outcome measures included Ostomy Adjustment Scale, Stoma Self-efficacy Scale, satisfaction with care, and stoma complications. Results of this study indicated that participants in the study group had significantly better ostomy adjustment, higher stoma self-efficacy, higher satisfaction with care, and less stoma complications compared with those in the control group. This study provided evidence to support that enterostomal nurse telephone follow-up can improve patient ostomy adjustment level and other related outcomes. Nurse telephone follow-up is an effective intervention to support the adjustment of stoma patients after hospital discharge.

Parenting and late adolescent emotional adjustment: mediating effects of discipline and gender.

PubMed

McKinney, Cliff; Milone, Mary Catherine; Renk, Kimberly

2011-08-01

Research suggests that parenting styles are related to the types of discipline parents utilize and that the coupling of parenting styles and discipline techniques are related to child outcomes. Although extant research examines the effects of parenting styles and discipline on child and early adolescent adjustment, less is known about adjustment in late adolescents, also described as emerging adults. Thus, the current study investigated the relationships among parenting styles (e.g., authoritative, authoritarian, permissive), discipline strategies (e.g., non-violent discipline, psychological aggression, physical assault), and emerging adult emotional adjustment (e.g., self-esteem, depression, and anxiety). The sample consisted of 526 participants ranging in age from 18 to 22 years. Results were analyzed with structural equation modeling and suggest that, although perceived parenting styles and discipline are both correlated with emerging adult emotional adjustment, perceived parenting is associated with emerging adult emotional adjustment for females but not males when examined simultaneously with perceived discipline. This finding demonstrates the importance of examining the direct and indirect relationships in the context of gender dyads.

On the Importance of Reliable Covariate Measurement in Selection Bias Adjustments Using Propensity Scores

ERIC Educational Resources Information Center

Steiner, Peter M.; Cook, Thomas D.; Shadish, William R.

2011-01-01

The effect of unreliability of measurement on propensity score (PS) adjusted treatment effects has not been previously studied. The authors report on a study simulating different degrees of unreliability in the multiple covariates that were used to estimate the PS. The simulation uses the same data as two prior studies. Shadish, Clark, and Steiner…

Double-adjustment in propensity score matching analysis: choosing a threshold for considering residual imbalance.

PubMed

Nguyen, Tri-Long; Collins, Gary S; Spence, Jessica; Daurès, Jean-Pierre; Devereaux, P J; Landais, Paul; Le Manach, Yannick

2017-04-28

Double-adjustment can be used to remove confounding if imbalance exists after propensity score (PS) matching. However, it is not always possible to include all covariates in adjustment. We aimed to find the optimal imbalance threshold for entering covariates into regression. We conducted a series of Monte Carlo simulations on virtual populations of 5,000 subjects. We performed PS 1:1 nearest-neighbor matching on each sample. We calculated standardized mean differences across groups to detect any remaining imbalance in the matched samples. We examined 25 thresholds (from 0.01 to 0.25, stepwise 0.01) for considering residual imbalance. The treatment effect was estimated using logistic regression that contained only those covariates considered to be unbalanced by these thresholds. We showed that regression adjustment could dramatically remove residual confounding bias when it included all of the covariates with a standardized difference greater than 0.10. The additional benefit was negligible when we also adjusted for covariates with less imbalance. We found that the mean squared error of the estimates was minimized under the same conditions. If covariate balance is not achieved, we recommend reiterating PS modeling until standardized differences below 0.10 are achieved on most covariates. In case of remaining imbalance, a double adjustment might be worth considering.

Global and regional estimates of the effectiveness and cost-effectiveness of price increases and other tobacco control policies.

PubMed

Ranson, M Kent; Jha, Prabhat; Chaloupka, Frank J; Nguyen, Son N

2002-08-01

The objective of this study was to provide conservative estimates of the global and regional effectiveness and cost-effectiveness of tobacco control policies. Using a static model of the cohort of smokers alive in 1995, we estimated the number of smoking-attributable deaths that could be averted by: (1) price increases, (2) nicotine replacement therapy (NRT), and (3) a package of non-price interventions other than NRT. We calculated the cost-effectiveness of these policy interventions by weighing the approximate public-sector costs against the years of healthy life saved, measured in disability-adjusted life years, or DALYs. Even with deliberately conservative assumptions, tax increases that would raise the real price of cigarettes by 10% worldwide would prevent between 5 and 16 million tobacco-related deaths, and could cost 3-70 US dollars per DALY saved in low-income and middle-income regions. NRT and a package of non-price interventions other than NRT are also cost-effective in low-income and middle-income regions, at 280-870 US dollars per DALY and 36-710 US dollars per DALY, respectively. In high-income countries, price increases were found to have a cost-effectiveness of 83-2771 US dollars per DALY, NRT 750-7206 US dollars per DALY and other non-price interventions 696-13,924 US dollars per DALY. Tobacco control policies, particularly tax increases on cigarettes, are cost-effective relative to other health interventions. Our estimates are subject to considerable variation in actual settings; thus, local cost-effectiveness studies are required to guide local policy.

Combined expectancies: electrophysiological evidence for the adjustment of expectancy effects

PubMed Central

Mattler, Uwe; van der Lugt, Arie; Münte, Thomas F

2006-01-01

Background When subjects use cues to prepare for a likely stimulus or a likely response, reaction times are facilitated by valid cues but prolonged by invalid cues. In studies on combined expectancy effects, two cues can independently give information regarding two dimensions of the forthcoming task. In certain situations, cueing effects on one dimension are reduced when the cue on the other dimension is invalid. According to the Adjusted Expectancy Model, cues affect different processing levels and a mechanism is presumed which is sensitive to the validity of early level cues and leads to online adjustment of expectancy effects at later levels. To examine the predictions of this model cueing of stimulus modality was combined with response cueing. Results Behavioral measures showed the interaction of cueing effects. Electrophysiological measures of the lateralized readiness potential (LRP) and the N200 amplitude confirmed the predictions of the model. The LRP showed larger effects of response cues on response activation when modality cues were valid rather than invalid. N200 amplitude was largest with valid modality cues and invalid response cues, medium with invalid modality cues, and smallest with two valid cues. Conclusion Findings support the view that the validity of early level expectancies modulates the effects of late level expectancies, which included response activation and response conflict in the present study. PMID:16674805

Adjusting for reverse causation to estimate the effect of obesity on mortality after incident heart failure in the Atherosclerosis Risk in Communities (ARIC) study.

PubMed

Shakiba, Maryam; Soori, Hamid; Mansournia, Mohammad Ali; Nazari, Seyed Saeed Hashemi; Salimi, Yahya

2016-01-01

The lower mortality rate of obese patients with heart failure (HF) has been partly attributed to reverse causation bias due to weight loss caused by disease. Using data about weight both before and after HF, this study aimed to adjust for reverse causation and examine the association of obesity both before and after HF with mortality. Using the Atherosclerosis Risk in Communities (ARIC) study, 308 patients with data available from before and after the incidence of HF were included. Pre-morbid and post-morbid obesity were defined based on body mass index measurements at least three months before and after incident HF. The associations of pre-morbid and post-morbid obesity and weight change with survival after HF were evaluated using a Cox proportional hazard model. Pre-morbid obesity was associated with higher mortality (hazard ratio [HR], 1.61; 95% confidence interval [CI], 1.04 to 2.49) but post-morbid obesity was associated with increased survival (HR, 0.57; 95% CI, 0.37 to 0.88). Adjusting for weight change due to disease as a confounder of the obesity-mortality relationship resulted in the absence of any significant associations between post-morbid obesity and mortality. This study demonstrated that controlling for reverse causality by adjusting for the confounder of weight change may remove or reverse the protective effect of obesity on mortality among patients with incident HF.

Implications of gambling problems for family and interpersonal adjustment: results from the Quinte Longitudinal Study.

PubMed

Cowlishaw, Sean; Suomi, Aino; Rodgers, Bryan

2016-09-01

To evaluate (1) whether gambling problems predict overall trajectories of change in family or interpersonal adjustment and (2) whether annual measures of gambling problems predict time-specific decreases in family or interpersonal adjustment, concurrently and prospectively. The Quinte Longitudinal Study (QLS) involved random-digit dialling of telephone numbers around the city of Belleville, Canada to recruit 'general population' and 'at-risk' groups (the latter oversampling people likely to develop problems). Five waves of assessment were conducted (2006-10). Latent Trajectory Modelling (LTM) estimated overall trajectories of family and interpersonal adjustment, which were predicted by gambling problems, and also estimated how time-specific problems predicted deviations from these trajectories. Southeast Ontario, Canada. Community sample of Canadian adults (n = 4121). The Problem Gambling Severity Index (PGSI) defined at-risk gambling (ARG: PGSI 1-2) and moderate-risk/problem gambling (MR/PG: PGSI 3+). Outcomes included: (1) family functioning, assessed using a seven-point rating of overall functioning; (2) social support, assessed using items from the Non-support subscale of the Personality Assessment Inventory; and (3) relationship satisfaction, measured by the Kansas Marital Satisfaction Scale. Baseline measures of ARG and MR/PG did not predict rates of change in trajectories of family or interpersonal adjustment. Rather, the annual measures of MR/PG predicted time-specific decreases in family functioning (estimate: -0.11, P < 0.01), social support (estimate: -0.28, P < 0.01) and relationship satisfaction (estimate: -0.53, P < 0.01). ARG predicted concurrent levels of family functioning (estimate: -0.07, P < 0.01). There were time-lagged effects of MR/PG on subsequent levels of family functioning (estimate: -0.12, P < 0.01) and social support (estimate: -0.24, P < 0.01). In a longitudinal study of Canadian adults, moderate

Adjusting health spending for the presence of comorbidities: an application to United States national inpatient data.

PubMed

Dieleman, Joseph L; Baral, Ranju; Johnson, Elizabeth; Bulchis, Anne; Birger, Maxwell; Bui, Anthony L; Campbell, Madeline; Chapin, Abigail; Gabert, Rose; Hamavid, Hannah; Horst, Cody; Joseph, Jonathan; Lomsadze, Liya; Squires, Ellen; Tobias, Martin

2017-08-29

One of the major challenges in estimating health care spending spent on each cause of illness is allocating spending for a health care event to a single cause of illness in the presence of comorbidities. Comorbidities, the secondary diagnoses, are common across many causes of illness and often correlate with worse health outcomes and more expensive health care. In this study, we propose a method for measuring the average spending for each cause of illness with and without comorbidities. Our strategy for measuring cause of illness-specific spending and adjusting for the presence of comorbidities uses a regression-based framework to estimate excess spending due to comorbidities. We consider multiple causes simultaneously, allowing causes of illness to appear as either a primary diagnosis or a comorbidity. Our adjustment method distributes excess spending away from primary diagnoses (outflows), exaggerated due to the presence of comorbidities, and allocates that spending towards causes of illness that appear as comorbidities (inflows). We apply this framework for spending adjustment to the National Inpatient Survey data in the United States for years 1996-2012 to generate comorbidity-adjusted health care spending estimates for 154 causes of illness by age and sex. The primary diagnoses with the greatest number of comorbidities in the NIS dataset were acute renal failure, septicemia, and endocarditis. Hypertension, diabetes, and ischemic heart disease were the most common comorbidities across all age groups. After adjusting for comorbidities, chronic kidney diseases, atrial fibrillation and flutter, and chronic obstructive pulmonary disease increased by 74.1%, 40.9%, and 21.0%, respectively, while pancreatitis, lower respiratory infections, and septicemia decreased by 21.3%, 17.2%, and 16.0%. For many diseases, comorbidity adjustments had varying effects on spending for different age groups. Our methodology takes a unified approach to account for excess spending caused

Validity of the estimates of oral cholera vaccine effectiveness derived from the test-negative design.

PubMed

Ali, Mohammad; You, Young Ae; Sur, Dipika; Kanungo, Suman; Kim, Deok Ryun; Deen, Jacqueline; Lopez, Anna Lena; Wierzba, Thomas F; Bhattacharya, Sujit K; Clemens, John D

2016-01-20

The test-negative design (TND) has emerged as a simple method for evaluating vaccine effectiveness (VE). Its utility for evaluating oral cholera vaccine (OCV) effectiveness is unknown. We examined this method's validity in assessing OCV effectiveness by comparing the results of TND analyses with those of conventional cohort analyses. Randomized controlled trials of OCV were conducted in Matlab (Bangladesh) and Kolkata (India), and an observational cohort design was used in Zanzibar (Tanzania). For all three studies, VE using the TND was estimated from the odds ratio (OR) relating vaccination status to fecal test status (Vibrio cholerae O1 positive or negative) among diarrheal patients enrolled during surveillance (VE= (1-OR)×100%). In cohort analyses of these studies, we employed the Cox proportional hazard model for estimating VE (=1-hazard ratio)×100%). OCV effectiveness estimates obtained using the TND (Matlab: 51%, 95% CI:37-62%; Kolkata: 67%, 95% CI:57-75%) were similar to the cohort analyses of these RCTs (Matlab: 52%, 95% CI:43-60% and Kolkata: 66%, 95% CI:55-74%). The TND VE estimate for the Zanzibar data was 94% (95% CI:84-98%) compared with 82% (95% CI:58-93%) in the cohort analysis. After adjusting for residual confounding in the cohort analysis of the Zanzibar study, using a bias indicator condition, we observed almost no difference in the two estimates. Our findings suggest that the TND is a valid approach for evaluating OCV effectiveness in routine vaccination programs. Copyright © 2015 Elsevier Ltd. All rights reserved.

Adjusted regression trend test for a multicenter clinical trial.

PubMed

Quan, H; Capizzi, T

1999-06-01

Studies using a series of increasing doses of a compound, including a zero dose control, are often conducted to study the effect of the compound on the response of interest. For a one-way design, Tukey et al. (1985, Biometrics 41, 295-301) suggested assessing trend by examining the slopes of regression lines under arithmetic, ordinal, and arithmetic-logarithmic dose scalings. They reported the smallest p-value for the three significance tests on the three slopes for safety assessments. Capizzi et al. (1992, Biometrical Journal 34, 275-289) suggested an adjusted trend test, which adjusts the p-value using a trivariate t-distribution, the joint distribution of the three slope estimators. In this paper, we propose an adjusted regression trend test suitable for two-way designs, particularly for multicenter clinical trials. In a step-down fashion, the proposed trend test can be applied to a multicenter clinical trial to compare each dose with the control. This sequential procedure is a closed testing procedure for a trend alternative. Therefore, it adjusts p-values and maintains experimentwise error rate. Simulation results show that the step-down trend test is overall more powerful than a step-down least significant difference test.

Effects of partial circadian adjustments on sleep and vigilance quality during simulated night work.

PubMed

Chapdelaine, Simon; Paquet, Jean; Dumont, Marie

2012-08-01

In most situations, complete circadian adjustment is not recommended for night workers. With complete adjustment, workers experience circadian misalignment when returning on a day-active schedule, causing repeated circadian phase shifts and internal desynchrony. For this reason, partial circadian realignment was proposed as a good compromise to stabilize internal circadian rhythms in night shift workers. However, the extent of partial circadian adjustment necessary to improve sleep and vigilance quality is still a matter of debate. In this study, the effects of small but statistically significant partial circadian adjustments on sleep and vigilance quality were assessed in a laboratory simulation of night work to determine whether they were also of clinical significance. Partial adjustments obtained by phase delay or by phase advance were quantified not only by the phase shift of dim light salivary melatonin onset, but also by the overlap of the episode of melatonin production with the sleep-wake cycle adopted during simulated night work. The effects on daytime sleep and night-time vigilance quality were modest. However, they suggest that even small adjustments by phase delay may decrease the accumulation of sleep debt, whereas the advance strategy improves subjective alertness and mood during night work. Furthermore, absolute phase shifts, by advance or by delay, were associated with improved subjective alertness and mood during the night shift. These strategies need to be tested in the field, to determine whether they can be adapted to real-life situations and provide effective support to night workers. © 2012 European Sleep Research Society.

Spatial variability effects on precision and power of forage yield estimation

USDA-ARS?s Scientific Manuscript database

Spatial analyses of yield trials are important, as they adjust cultivar means for spatial variation and improve the statistical precision of yield estimation. While the relative efficiency of spatial analysis has been frequently reported in several yield trials, its application on long-term forage y...

Effect of gender on psychosocial adjustment of colorectal cancer survivors with ostomy.

PubMed

Gautam, Sital; Poudel, Anju

2016-12-01

Stoma can pose extensive challenges for colorectal cancer survivors. Identifying the psychological and social adjustment among them and how it differs by gender will aid in identifying those particularly at risk of having poor adjustment and in planning programs to improve their adjustment. The purpose of this study was to determine the effect of gender on psychosocial adjustment of colorectal cancer survivors with ostomy. A descriptive cross sectional study was carried out in the stoma clinic of B.P. Koirala Memorial Cancer Hospital, Bharatpur, Nepal. A purposive sample of 122 patients with ostomy was taken from the above mentioned setting. Selection criteria included colorectal cancer survivors having ostomy for at least 6 months. Data on socio-demographic and clinical variables were collected. Psychosocial adjustment was measured using Ostomy Adjustment Inventory-23 (OAI-23). A total of 122 patients were included in the study. Mean time since ostomy surgery was 2.53 and 1.98 years for men and women respectively. Both men and women had significant impairment in the psychosocial adjustment, however, men had significantly lower psychosocial adjustment score (37.68±12.96 vs . 43.45±12.81, t=-2.47, P=0.015) at 95% CI as compared to women and they reported more negative emotions. Furthermore, men significantly predicted low acceptance {β=-3.078, P=0.023, ΔR 2 =0.036, F [4,117] =7.90, P<0.001} and social engagement score {β=-2.501, P<0.001, ΔR 2 =0.098, F [4,117] =6.03, P<0.001}. Colorectal cancer survivors with ostomy should be monitored for psychosocial concerns in regular basis and health care providers should tailor care based on their need. Approaches of survivorship care and psychosocial interventions in colorectal cancer survivors with ostomy should take into account gender specific concerns and requirements to aid adjustment.

The Bivalency Effect: Evidence for Flexible Adjustment of Cognitive Control

ERIC Educational Resources Information Center

Rey-Mermet, Alodie; Meier, Beat

2012-01-01

When bivalent stimuli (i.e., stimuli with features for two different tasks) appear occasionally, performance is slower on subsequent univalent stimuli. This "bivalency effect" reflects an adjustment of cognitive control arising from the more demanding context created by bivalent stimuli. So far, it has been investigated only on task…

Analysis of adjusting effects of mounting force on frequency conversion of mounted nonlinear optics.

PubMed

Su, Ruifeng; Liu, Haitao; Liang, Yingchun; Lu, Lihua

2014-01-10

Motivated by the need to increase the second harmonic generation (SHG) efficiency of nonlinear optics with large apertures, a novel mounting configuration with active adjusting function on the SHG efficiency is proposed and mechanically and optically studied. The adjusting effects of the mounting force on the distortion and stress are analyzed by the finite element methods (FEM), as well as the contribution of the distortion and stress to the change in phase mismatch, and the SHG efficiency are theoretically stated. Further on, the SHG efficiency is calculated as a function of the mounting force. The changing trends of the distortion, stress, and the SHG efficiency with the varying mounting force are obtained, and the optimal ones are figured out. Moreover, the mechanism of the occurrence of the optimal values is studied and the adjusting strategy is put forward. Numerical results show the robust adjustment of the mounting force, as well as the effectiveness of the mounting configuration, in increasing the SHG efficiency.

Assessing the performance of the generalized propensity score for estimating the effect of quantitative or continuous exposures on survival or time-to-event outcomes.

PubMed

Austin, Peter C

2018-01-01

Propensity score methods are frequently used to estimate the effects of interventions using observational data. The propensity score was originally developed for use with binary exposures. The generalized propensity score (GPS) is an extension of the propensity score for use with quantitative or continuous exposures (e.g. pack-years of cigarettes smoked, dose of medication, or years of education). We describe how the GPS can be used to estimate the effect of continuous exposures on survival or time-to-event outcomes. To do so we modified the concept of the dose-response function for use with time-to-event outcomes. We used Monte Carlo simulations to examine the performance of different methods of using the GPS to estimate the effect of quantitative exposures on survival or time-to-event outcomes. We examined covariate adjustment using the GPS and weighting using weights based on the inverse of the GPS. The use of methods based on the GPS was compared with the use of conventional G-computation and weighted G-computation. Conventional G-computation resulted in estimates of the dose-response function that displayed the lowest bias and the lowest variability. Amongst the two GPS-based methods, covariate adjustment using the GPS tended to have the better performance. We illustrate the application of these methods by estimating the effect of average neighbourhood income on the probability of survival following hospitalization for an acute myocardial infarction.

Affordable Care Act risk adjustment: overview, context, and challenges.

PubMed

Kautter, John; Pope, Gregory C; Keenan, Patricia

2014-01-01

Beginning in 2014, individuals and small businesses will be able to purchase private health insurance through competitive marketplaces. The Affordable Care Act (ACA) provides for a program of risk adjustment in the individual and small group markets in 2014 as Marketplaces are implemented and new market reforms take effect. The purpose of risk adjustment is to lessen or eliminate the influence of risk selection on the premiums that plans charge and the incentive for plans to avoid sicker enrollees. This article--the first of three in the Medicare & Medicaid Research Review--describes the key program goal and issues in the Department of Health and Human Services (HHS) developed risk adjustment methodology, and identifies key choices in how the methodology responds to these issues. The goal of the HHS risk adjustment methodology is to compensate health insurance plans for differences in enrollee health mix so that plan premiums reflect differences in scope of coverage and other plan factors, but not differences in health status. The methodology includes a risk adjustment model and a risk transfer formula that together address this program goal as well as three issues specific to ACA risk adjustment: 1) new population; 2) cost and rating factors; and 3) balanced transfers within state/market. The risk adjustment model, described in the second article, estimates differences in health risks taking into account the new population and scope of coverage (actuarial value level). The transfer formula, described in the third article, calculates balanced transfers that are intended to account for health risk differences while preserving permissible premium differences.

Appraisal and coping as mediators of the effects of cumulative risk on preadolescent adjustment

PubMed Central

Thompson, Stephanie F.; Lengua, Liliana J.; Garcia, Connie Meza

2016-01-01

This study examined the concurrent and longitudinal relations among cumulative risk, appraisal, coping, and adjustment. Longitudinal path models were tested in a community sample of 316 children in preadolescence to examine hypotheses that threat appraisal and avoidant coping mediate the effects of cumulative risk on child adjustment, whereas positive appraisal and active coping were hypothesized to predict better adjustment independently. Children and their mothers were assessed during in-home interviews at three time points at one-year intervals. Children reported on appraisal and coping strategies. Mothers and children reported on child adjustment problems and positive adjustment. Rank-order changes in appraisal and coping predicted rank-order changes in adjustment. Cumulative risk was concurrently related to higher threat appraisal and avoidant coping at each time point. Threat appraisal and avoidant coping mediated the relations of cumulative risk to rank-order changes in adjustment. There is specificity in the relations of cumulative risk to threat appraisal and avoidant coping, whereas positive appraisal and active coping are independent of risk and operate as individual resource factors. PMID:27110087

Adjusting for treatment switching in randomised controlled trials - A simulation study and a simplified two-stage method.

PubMed

Latimer, Nicholas R; Abrams, K R; Lambert, P C; Crowther, M J; Wailoo, A J; Morden, J P; Akehurst, R L; Campbell, M J

2017-04-01

Estimates of the overall survival benefit of new cancer treatments are often confounded by treatment switching in randomised controlled trials (RCTs) - whereby patients randomised to the control group are permitted to switch onto the experimental treatment upon disease progression. In health technology assessment, estimates of the unconfounded overall survival benefit associated with the new treatment are needed. Several switching adjustment methods have been advocated in the literature, some of which have been used in health technology assessment. However, it is unclear which methods are likely to produce least bias in realistic RCT-based scenarios. We simulated RCTs in which switching, associated with patient prognosis, was permitted. Treatment effect size and time dependency, switching proportions and disease severity were varied across scenarios. We assessed the performance of alternative adjustment methods based upon bias, coverage and mean squared error, related to the estimation of true restricted mean survival in the absence of switching in the control group. We found that when the treatment effect was not time-dependent, rank preserving structural failure time models (RPSFTM) and iterative parameter estimation methods produced low levels of bias. However, in the presence of a time-dependent treatment effect, these methods produced higher levels of bias, similar to those produced by an inverse probability of censoring weights method. The inverse probability of censoring weights and structural nested models produced high levels of bias when switching proportions exceeded 85%. A simplified two-stage Weibull method produced low bias across all scenarios and provided the treatment switching mechanism is suitable, represents an appropriate adjustment method.

A Machine Learning Framework for Plan Payment Risk Adjustment.

PubMed

Rose, Sherri

2016-12-01

To introduce cross-validation and a nonparametric machine learning framework for plan payment risk adjustment and then assess whether they have the potential to improve risk adjustment. 2011-2012 Truven MarketScan database. We compare the performance of multiple statistical approaches within a broad machine learning framework for estimation of risk adjustment formulas. Total annual expenditure was predicted using age, sex, geography, inpatient diagnoses, and hierarchical condition category variables. The methods included regression, penalized regression, decision trees, neural networks, and an ensemble super learner, all in concert with screening algorithms that reduce the set of variables considered. The performance of these methods was compared based on cross-validated R 2 . Our results indicate that a simplified risk adjustment formula selected via this nonparametric framework maintains much of the efficiency of a traditional larger formula. The ensemble approach also outperformed classical regression and all other algorithms studied. The implementation of cross-validated machine learning techniques provides novel insight into risk adjustment estimation, possibly allowing for a simplified formula, thereby reducing incentives for increased coding intensity as well as the ability of insurers to "game" the system with aggressive diagnostic upcoding. © Health Research and Educational Trust.

15 CFR 90.16 - Notification of adjustment.

Code of Federal Regulations, 2011 CFR

2011-01-01

... CENSUS, DEPARTMENT OF COMMERCE PROCEDURE FOR CHALLENGING CERTAIN POPULATION AND INCOME ESTIMATES § 90.16 Notification of adjustment. In the event that the Director finds that the population or per capita income...

15 CFR 90.16 - Notification of adjustment.

Code of Federal Regulations, 2010 CFR

2010-01-01

... CENSUS, DEPARTMENT OF COMMERCE PROCEDURE FOR CHALLENGING CERTAIN POPULATION AND INCOME ESTIMATES § 90.16 Notification of adjustment. In the event that the Director finds that the population or per capita income...

15 CFR 90.16 - Notification of adjustment.

Code of Federal Regulations, 2012 CFR

2012-01-01

... CENSUS, DEPARTMENT OF COMMERCE PROCEDURE FOR CHALLENGING CERTAIN POPULATION AND INCOME ESTIMATES § 90.16 Notification of adjustment. In the event that the Director finds that the population or per capita income...

15 CFR 90.16 - Notification of adjustment.

Code of Federal Regulations, 2013 CFR

2013-01-01

... CENSUS, DEPARTMENT OF COMMERCE PROCEDURE FOR CHALLENGING CERTAIN POPULATION AND INCOME ESTIMATES § 90.16 Notification of adjustment. In the event that the Director finds that the population or per capita income...

Estimating vaccine effectiveness against severe influenza in England and Scotland 2011/2012: applying the screening method to data from intensive care surveillance systems.

PubMed

Thomas, H L; Andrews, N; Green, H K; Boddington, N L; Zhao, H; Reynolds, A; McMenamin, J; Pebody, R G

2014-01-01

Methods for estimating vaccine effectiveness (VE) against severe influenza are not well established. We used the screening method to estimate VE against influenza resulting in intensive care unit (ICU) admission in England and Scotland in 2011/2012. We extracted data on confirmed influenza ICU cases from severe influenza surveillance systems, and obtained their 2011/2012 trivalent influenza vaccine (TIV) status from primary care. We compared case vaccine uptake with population vaccine uptake obtained from routine monitoring systems, adjusting for age group, specific risk group, region and week. Of 60 influenza ICU cases reported, vaccination status was available for 56 (93%). Adjusted VE against ICU admission for those aged ≥ 65 years was -10% [95% confidence interval (CI) -207 to 60], consistent with evidence of poor protection from the 2011/2012 TIV in 2011/2012. Adjusted VE for those aged <65 years in risk groups was -296% (95% CI -930 to -52), suggesting significant residual confounding using the screening method in those subject to selective vaccination.

Inter-provider comparison of patient-reported outcomes: developing an adjustment to account for differences in patient case mix.

PubMed

Nuttall, David; Parkin, David; Devlin, Nancy

2015-01-01

This paper describes the development of a methodology for the case-mix adjustment of patient-reported outcome measures (PROMs) data permitting the comparison of outcomes between providers on a like-for-like basis. Statistical models that take account of provider-specific effects form the basis of the proposed case-mix adjustment methodology. Indirect standardisation provides a transparent means of case mix adjusting the PROMs data, which are updated on a monthly basis. Recently published PROMs data for patients undergoing unilateral knee replacement are used to estimate empirical models and to demonstrate the application of the proposed case-mix adjustment methodology in practice. The results are illustrative and are used to highlight a number of theoretical and empirical issues that warrant further exploration. For example, because of differences between PROMs instruments, case-mix adjustment methodologies may require instrument-specific approaches. A number of key assumptions are made in estimating the empirical models, which could be open to challenge. The covariates of post-operative health status could be expanded, and alternative econometric methods could be employed. © 2013 Crown copyright.

Effect of gender on psychosocial adjustment of colorectal cancer survivors with ostomy

PubMed Central

Poudel, Anju

2016-01-01

Background Stoma can pose extensive challenges for colorectal cancer survivors. Identifying the psychological and social adjustment among them and how it differs by gender will aid in identifying those particularly at risk of having poor adjustment and in planning programs to improve their adjustment. The purpose of this study was to determine the effect of gender on psychosocial adjustment of colorectal cancer survivors with ostomy. Methods A descriptive cross sectional study was carried out in the stoma clinic of B.P. Koirala Memorial Cancer Hospital, Bharatpur, Nepal. A purposive sample of 122 patients with ostomy was taken from the above mentioned setting. Selection criteria included colorectal cancer survivors having ostomy for at least 6 months. Data on socio-demographic and clinical variables were collected. Psychosocial adjustment was measured using Ostomy Adjustment Inventory-23 (OAI-23). Results A total of 122 patients were included in the study. Mean time since ostomy surgery was 2.53 and 1.98 years for men and women respectively. Both men and women had significant impairment in the psychosocial adjustment, however, men had significantly lower psychosocial adjustment score (37.68±12.96 vs. 43.45±12.81, t=−2.47, P=0.015) at 95% CI as compared to women and they reported more negative emotions. Furthermore, men significantly predicted low acceptance {β=−3.078, P=0.023, ΔR2=0.036, F [4,117] =7.90, P<0.001} and social engagement score {β=−2.501, P<0.001, ΔR2=0.098, F [4,117] =6.03, P<0.001}. Conclusions Colorectal cancer survivors with ostomy should be monitored for psychosocial concerns in regular basis and health care providers should tailor care based on their need. Approaches of survivorship care and psychosocial interventions in colorectal cancer survivors with ostomy should take into account gender specific concerns and requirements to aid adjustment. PMID:28078117

Deep space network software cost estimation model

NASA Technical Reports Server (NTRS)

Tausworthe, R. C.

1981-01-01

A parametric software cost estimation model prepared for Jet PRopulsion Laboratory (JPL) Deep Space Network (DSN) Data System implementation tasks is described. The resource estimation mdel modifies and combines a number of existing models. The model calibrates the task magnitude and difficulty, development environment, and software technology effects through prompted responses to a set of approximately 50 questions. Parameters in the model are adjusted to fit JPL software life-cycle statistics.

Estimating mean QALYs in trial-based cost-effectiveness analysis: the importance of controlling for baseline utility.

PubMed

Manca, Andrea; Hawkins, Neil; Sculpher, Mark J

2005-05-01

In trial-based cost-effectiveness analysis baseline mean utility values are invariably imbalanced between treatment arms. A patient's baseline utility is likely to be highly correlated with their quality-adjusted life-years (QALYs) over the follow-up period, not least because it typically contributes to the QALY calculation. Therefore, imbalance in baseline utility needs to be accounted for in the estimation of mean differential QALYs, and failure to control for this imbalance can result in a misleading incremental cost-effectiveness ratio. This paper discusses the approaches that have been used in the cost-effectiveness literature to estimate absolute and differential mean QALYs alongside randomised trials, and illustrates the implications of baseline mean utility imbalance for QALY calculation. Using data from a recently conducted trial-based cost-effectiveness study and a micro-simulation exercise, the relative performance of alternative estimators is compared, showing that widely used methods to calculate differential QALYs provide incorrect results in the presence of baseline mean utility imbalance regardless of whether these differences are formally statistically significant. It is demonstrated that multiple regression methods can be usefully applied to generate appropriate estimates of differential mean QALYs and an associated measure of sampling variability, while controlling for differences in baseline mean utility between treatment arms in the trial. Copyright 2004 John Wiley & Sons, Ltd

Using surveillance data to estimate pandemic vaccine effectiveness against laboratory confirmed influenza A(H1N1)2009 infection: two case-control studies, Spain, season 2009-2010

PubMed Central

2011-01-01

Background Physicians of the Spanish Influenza Sentinel Surveillance System report and systematically swab patients attended to their practices for influenza-like illness (ILI). Within the surveillance system, some Spanish regions also participated in an observational study aiming at estimating influenza vaccine effectiveness (cycEVA study). During the season 2009-2010, we estimated pandemic influenza vaccine effectiveness using both the influenza surveillance data and the cycEVA study. Methods We conducted two case-control studies using the test-negative design, between weeks 48/2009 and 8/2010 of the pandemic season. The surveillance-based study included all swabbed patients in the sentinel surveillance system. The cycEVA study included swabbed patients from seven Spanish regions. Cases were laboratory-confirmed pandemic influenza A(H1N1)2009. Controls were ILI patients testing negative for any type of influenza. Variables collected in both studies included demographic data, vaccination status, laboratory results, chronic conditions, and pregnancy. Additionally, cycEVA questionnaire collected data on previous influenza vaccination, smoking, functional status, hospitalisations, visits to the general practitioners, and obesity. We used logistic regression to calculate adjusted odds ratios (OR), computing pandemic influenza vaccine effectiveness as (1-OR)*100. Results We included 331 cases and 995 controls in the surveillance-based study and 85 cases and 351 controls in the cycEVA study. We detected nine (2.7%) and two (2.4%) vaccine failures in the surveillance-based and cycEVA studies, respectively. Adjusting for variables collected in surveillance database and swabbing month, pandemic influenza vaccine effectiveness was 62% (95% confidence interval (CI): -5; 87). The cycEVA vaccine effectiveness was 64% (95%CI: -225; 96) when adjusting for common variables with the surveillance system and 75% (95%CI: -293; 98) adjusting for all variables collected. Conclusion

Relations between aggression and adjustment in chinese children: moderating effects of academic achievement.

PubMed

Yang, Fan; Chen, Xinyin; Wang, Li

2014-01-01

The primary purpose of the study was to examine the moderating effects of academic achievement on relations between aggressive behavior and social and psychological adjustment in Chinese children. A sample of children (N = 1,171; 591 boys, 580 girls; initial M age = 9 years) in China participated in the study. Two waves of longitudinal data were collected in Grades 3 and 4 from multiple sources including peer nominations, teacher ratings, self-reports, and school records. The results indicated that the main effects of aggression on adjustment were more evident than those of adjustment on aggression. Moreover, aggression was negatively associated with later leadership status and positively associated with later peer victimization, mainly for high-achieving children. The results suggested that consistent with the resource-potentiating model, academic achievement served to enhance the positive development of children with low aggression. On the other hand, although the findings indicated fewer main effects of adjustment on aggression, loneliness, depression, and perceived social incompetence positively predicted later aggression for low-achieving, but not high-achieving, children, which suggested that consistent with the stress-buffering model, academic achievement protected children with psychological difficulties from developing aggressive behavior. The results indicate that academic achievement is involved in behavioral and socioemotional development in different manners in Chinese children. Researchers should consider an integrative approach based on children's behavioral, psychological, and academic functions in designing prevention and intervention programs.

Smartphone Addiction and School Life Adjustment Among High School Students: The Mediating Effect of Self-Control.

PubMed

Heo, YoungJin; Lee, Kyunghee

2018-05-08

Previous studies have reported associations among smartphone addiction, school adjustment, and self-control. However, the causal relationship between smartphone addiction and school adjustment has not been clearly demonstrated. The current study examined the association between smartphone addiction and school adjustment and investigated the mediating effect of self-control in this association. A total of 790 students from five high schools in Daegu City, South Korea, were asked to provide demographic information and complete a self-diagnostic smartphone addiction scale and validated Korean version of a self-control scale. Among at-risk students, self-control did not mediate the relation between smartphone addiction and school adjustment; among those not at risk, there was a partial mediating effect. To improve school adjustment among high school students, prevention of smartphone addiction seems important. Smartphone addiction could be managed by strengthening self-control to promote healthy use of smartphones. The current results can serve as groundwork for the development of programs to improve school adjustment among high school students. [Journal of Psychosocial Nursing and Mental Health Services, xx(x), xx-xx.]. Copyright 2018, SLACK Incorporated.

Environmental Chemicals in Urine and Blood: Improving Methods for Creatinine and Lipid Adjustment.

PubMed

O'Brien, Katie M; Upson, Kristen; Cook, Nancy R; Weinberg, Clarice R

2016-02-01

Investigators measuring exposure biomarkers in urine typically adjust for creatinine to account for dilution-dependent sample variation in urine concentrations. Similarly, it is standard to adjust for serum lipids when measuring lipophilic chemicals in serum. However, there is controversy regarding the best approach, and existing methods may not effectively correct for measurement error. We compared adjustment methods, including novel approaches, using simulated case-control data. Using a directed acyclic graph framework, we defined six causal scenarios for epidemiologic studies of environmental chemicals measured in urine or serum. The scenarios include variables known to influence creatinine (e.g., age and hydration) or serum lipid levels (e.g., body mass index and recent fat intake). Over a range of true effect sizes, we analyzed each scenario using seven adjustment approaches and estimated the corresponding bias and confidence interval coverage across 1,000 simulated studies. For urinary biomarker measurements, our novel method, which incorporates both covariate-adjusted standardization and the inclusion of creatinine as a covariate in the regression model, had low bias and possessed 95% confidence interval coverage of nearly 95% for most simulated scenarios. For serum biomarker measurements, a similar approach involving standardization plus serum lipid level adjustment generally performed well. To control measurement error bias caused by variations in serum lipids or by urinary diluteness, we recommend improved methods for standardizing exposure concentrations across individuals.

Quantifying the causal effects of 20mph zones on road casualties in London via doubly robust estimation.

PubMed

Li, Haojie; Graham, Daniel J

2016-08-01

This paper estimates the causal effect of 20mph zones on road casualties in London. Potential confounders in the key relationship of interest are included within outcome regression and propensity score models, and the models are then combined to form a doubly robust estimator. A total of 234 treated zones and 2844 potential control zones are included in the data sample. The propensity score model is used to select a viable control group which has common support in the covariate distributions. We compare the doubly robust estimates with those obtained using three other methods: inverse probability weighting, regression adjustment, and propensity score matching. The results indicate that 20mph zones have had a significant causal impact on road casualty reduction in both absolute and proportional terms. Copyright © 2016 Elsevier Ltd. All rights reserved.

Relative Pose Estimation Using Image Feature Triplets

NASA Astrophysics Data System (ADS)

Chuang, T. Y.; Rottensteiner, F.; Heipke, C.

2015-03-01

A fully automated reconstruction of the trajectory of image sequences using point correspondences is turning into a routine practice. However, there are cases in which point features are hardly detectable, cannot be localized in a stable distribution, and consequently lead to an insufficient pose estimation. This paper presents a triplet-wise scheme for calibrated relative pose estimation from image point and line triplets, and investigates the effectiveness of the feature integration upon the relative pose estimation. To this end, we employ an existing point matching technique and propose a method for line triplet matching in which the relative poses are resolved during the matching procedure. The line matching method aims at establishing hypotheses about potential minimal line matches that can be used for determining the parameters of relative orientation (pose estimation) of two images with respect to the reference one; then, quantifying the agreement using the estimated orientation parameters. Rather than randomly choosing the line candidates in the matching process, we generate an associated lookup table to guide the selection of potential line matches. In addition, we integrate the homologous point and line triplets into a common adjustment procedure. In order to be able to also work with image sequences the adjustment is formulated in an incremental manner. The proposed scheme is evaluated with both synthetic and real datasets, demonstrating its satisfactory performance and revealing the effectiveness of image feature integration.

The Effectiveness of Using Limited Gauge Measurements for Bias Adjustment of Satellite-Based Precipitation Estimation over Saudi Arabia

NASA Astrophysics Data System (ADS)

Alharbi, Raied; Hsu, Kuolin; Sorooshian, Soroosh; Braithwaite, Dan

2018-01-01

Precipitation is a key input variable for hydrological and climate studies. Rain gauges are capable of providing reliable precipitation measurements at point scale. However, the uncertainty of rain measurements increases when the rain gauge network is sparse. Satellite -based precipitation estimations appear to be an alternative source of precipitation measurements, but they are influenced by systematic bias. In this study, a method for removing the bias from the Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks-Cloud Classification System (PERSIANN-CCS) over a region where the rain gauge is sparse is investigated. The method consists of monthly empirical quantile mapping, climate classification, and inverse-weighted distance method. Daily PERSIANN-CCS is selected to test the capability of the method for removing the bias over Saudi Arabia during the period of 2010 to 2016. The first six years (2010 - 2015) are calibrated years and 2016 is used for validation. The results show that the yearly correlation coefficient was enhanced by 12%, the yearly mean bias was reduced by 93% during validated year. Root mean square error was reduced by 73% during validated year. The correlation coefficient, the mean bias, and the root mean square error show that the proposed method removes the bias on PERSIANN-CCS effectively that the method can be applied to other regions where the rain gauge network is sparse.

COMPARATIVE EFFECTIVENESS OF AN ADJUSTABLE TRANSFEMORAL PROSTHETIC INTERFACE ACCOMMODATING VOLUME FLUCTUATION: CASE STUDY

PubMed Central

Kahle, Jason T.; Klenow, Tyler D.; Highsmith, M. Jason

2016-01-01

The socket-limb interface is vital for functionality and provides stability and mobility for the amputee. Volume fluctuation can lead to compromised fit and function. Current socket technology does not accommodate for volume fluctuation. An adjustable interface may improve function and comfort by filling this technology gap. The purpose of this study was to compare the effectiveness of the standard of care (SOC) ischial ramus containment to an adjustable transfemoral prosthetic interface socket in the accommodation of volume fluctuation. A prospective experimental case study using repeated measures of subjective and performance outcome measures between socket conditions was employed. In the baseline volume condition, the adjustable socket improved subjective and performance measures 19% to 37% over SOC, whereas the two-minute walk test demonstrated equivalence. In the volume loss condition, the adjustable socket improved all subjective and performance measures 22% to 93%. All aggregated data improved 16% to 50% compared with the SOC. In simulated volume gain, the SOC socket failed, while the subject was able to complete the protocol using the adjustable socket. In this case study, the SOC socket was inferior to the comparative adjustable transfemoral amputation interface in subjective and performance outcomes. There is a lack of clinical trials and evidence comparing socket functional outcomes related to volume fluctuation. PMID:28066526

Estimation of effective wind speed

NASA Astrophysics Data System (ADS)

Østergaard, K. Z.; Brath, P.; Stoustrup, J.

2007-07-01

The wind speed has a huge impact on the dynamic response of wind turbine. Because of this, many control algorithms use a measure of the wind speed to increase performance, e.g. by gain scheduling and feed forward. Unfortunately, no accurate measurement of the effective wind speed is online available from direct measurements, which means that it must be estimated in order to make such control methods applicable in practice. In this paper a new method is presented for the estimation of the effective wind speed. First, the rotor speed and aerodynamic torque are estimated by a combined state and input observer. These two variables combined with the measured pitch angle is then used to calculate the effective wind speed by an inversion of a static aerodynamic model.

Acute health impacts of airborne particles estimated from satellite remote sensing.

PubMed

Wang, Zhaoxi; Liu, Yang; Hu, Mu; Pan, Xiaochuan; Shi, Jing; Chen, Feng; He, Kebin; Koutrakis, Petros; Christiani, David C

2013-01-01

Satellite-based remote sensing provides a unique opportunity to monitor air quality from space at global, continental, national and regional scales. Most current research focused on developing empirical models using ground measurements of the ambient particulate. However, the application of satellite-based exposure assessment in environmental health is still limited, especially for acute effects, because the development of satellite PM(2.5) model depends on the availability of ground measurements. We tested the hypothesis that MODIS AOD (aerosol optical depth) exposure estimates, obtained from NASA satellites, are directly associated with daily health outcomes. Three independent healthcare databases were used: unscheduled outpatient visits, hospital admissions, and mortality collected in Beijing metropolitan area, China during 2006. We use generalized linear models to compare the short-term effects of air pollution assessed by ground monitoring (PM(10)) with adjustment of absolute humidity (AH) and AH-calibrated AOD. Across all databases we found that both AH-calibrated AOD and PM(10) (adjusted by AH) were consistently associated with elevated daily events on the current day and/or lag days for cardiovascular diseases, ischemic heart diseases, and COPD. The relative risks estimated by AH-calibrated AOD and PM(10) (adjusted by AH) were similar. Additionally, compared to ground PM(10), we found that AH-calibrated AOD had narrower confidence intervals for all models and was more robust in estimating the current day and lag day effects. Our preliminary findings suggested that, with proper adjustment of meteorological factors, satellite AOD can be used directly to estimate the acute health impacts of ambient particles without prior calibrating to the sparse ground monitoring networks. Copyright © 2012 Elsevier Ltd. All rights reserved.

Adjusting for overdispersion in piecewise exponential regression models to estimate excess mortality rate in population-based research.

PubMed

Luque-Fernandez, Miguel Angel; Belot, Aurélien; Quaresma, Manuela; Maringe, Camille; Coleman, Michel P; Rachet, Bernard

2016-10-01

In population-based cancer research, piecewise exponential regression models are used to derive adjusted estimates of excess mortality due to cancer using the Poisson generalized linear modelling framework. However, the assumption that the conditional mean and variance of the rate parameter given the set of covariates x i are equal is strong and may fail to account for overdispersion given the variability of the rate parameter (the variance exceeds the mean). Using an empirical example, we aimed to describe simple methods to test and correct for overdispersion. We used a regression-based score test for overdispersion under the relative survival framework and proposed different approaches to correct for overdispersion including a quasi-likelihood, robust standard errors estimation, negative binomial regression and flexible piecewise modelling. All piecewise exponential regression models showed the presence of significant inherent overdispersion (p-value <0.001). However, the flexible piecewise exponential model showed the smallest overdispersion parameter (3.2 versus 21.3) for non-flexible piecewise exponential models. We showed that there were no major differences between methods. However, using a flexible piecewise regression modelling, with either a quasi-likelihood or robust standard errors, was the best approach as it deals with both, overdispersion due to model misspecification and true or inherent overdispersion.

The performance of different propensity score methods for estimating marginal hazard ratios.

PubMed

Austin, Peter C

2013-07-20

Propensity score methods are increasingly being used to reduce or minimize the effects of confounding when estimating the effects of treatments, exposures, or interventions when using observational or non-randomized data. Under the assumption of no unmeasured confounders, previous research has shown that propensity score methods allow for unbiased estimation of linear treatment effects (e.g., differences in means or proportions). However, in biomedical research, time-to-event outcomes occur frequently. There is a paucity of research into the performance of different propensity score methods for estimating the effect of treatment on time-to-event outcomes. Furthermore, propensity score methods allow for the estimation of marginal or population-average treatment effects. We conducted an extensive series of Monte Carlo simulations to examine the performance of propensity score matching (1:1 greedy nearest-neighbor matching within propensity score calipers), stratification on the propensity score, inverse probability of treatment weighting (IPTW) using the propensity score, and covariate adjustment using the propensity score to estimate marginal hazard ratios. We found that both propensity score matching and IPTW using the propensity score allow for the estimation of marginal hazard ratios with minimal bias. Of these two approaches, IPTW using the propensity score resulted in estimates with lower mean squared error when estimating the effect of treatment in the treated. Stratification on the propensity score and covariate adjustment using the propensity score result in biased estimation of both marginal and conditional hazard ratios. Applied researchers are encouraged to use propensity score matching and IPTW using the propensity score when estimating the relative effect of treatment on time-to-event outcomes. Copyright © 2012 John Wiley & Sons, Ltd.

The test-negative design for estimating influenza vaccine effectiveness.

PubMed

Jackson, Michael L; Nelson, Jennifer C

2013-04-19

The test-negative design has emerged in recent years as the preferred method for estimating influenza vaccine effectiveness (VE) in observational studies. However, the methodologic basis of this design has not been formally developed. In this paper we develop the rationale and underlying assumptions of the test-negative study. Under the test-negative design for influenza VE, study subjects are all persons who seek care for an acute respiratory illness (ARI). All subjects are tested for influenza infection. Influenza VE is estimated from the ratio of the odds of vaccination among subjects testing positive for influenza to the odds of vaccination among subjects testing negative. With the assumptions that (a) the distribution of non-influenza causes of ARI does not vary by influenza vaccination status, and (b) VE does not vary by health care-seeking behavior, the VE estimate from the sample can generalized to the full source population that gave rise to the study sample. Based on our derivation of this design, we show that test-negative studies of influenza VE can produce biased VE estimates if they include persons seeking care for ARI when influenza is not circulating or do not adjust for calendar time. The test-negative design is less susceptible to bias due to misclassification of infection and to confounding by health care-seeking behavior, relative to traditional case-control or cohort studies. The cost of the test-negative design is the additional, difficult-to-test assumptions that incidence of non-influenza respiratory infections is similar between vaccinated and unvaccinated groups within any stratum of care-seeking behavior, and that influenza VE does not vary across care-seeking strata. Copyright © 2013 Elsevier Ltd. All rights reserved.

The effect of somatic cell count data adjustment and interpretation, as outlined in European Union legislation, on herd eligibility to supply raw milk for processing of dairy products.

PubMed

More, S J; Clegg, T A; Lynch, P J; O'Grady, L

2013-06-01

Somatic cell count (SCC) limits are a key component of national and international regulation for milk quality. As yet, very limited work has been published on SCC regulatory standards, including on the effect of different approaches to SCC data adjustment and interpretation. This study examines the effect of SCC data adjustment and interpretation, as outlined in current European Union (EU) legislation, on herd eligibility to supply raw milk for processing of dairy products for human consumption, using Irish data for illustration. The study used Irish milk-recording data as a proxy for bulk tank SCC (BTSCC) data, to calculate an unadjusted monthly SCC value for each herd during each month of participation. Subsequently, 4 data adjustments were applied, as outlined in EU and national legislation: seasonal adjustment; 3-mo rolling geometric average, without accounting for a break in the supply; 3-mo rolling geometric average, after accounting for a break in the supply; and seasonal adjustment and 3-mo rolling geometric average combined, after accounting for a break in the supply. Analyses were conducted to examine the effect, during the period from 2004 to 2010, of data adjustment on the percentage of herds with herd SCC >400,000 cells/mL. In all, 4 interpretation scenarios, incorporating different data adjustment combinations, were used to estimate herd eligibility (compliant, under warning, or suspended, as defined by legislation) to supply raw milk for processing. The 4 methods of data adjustment each led to a sizable reduction (6.7, 5.0, 5.3, and 11.1 percentage points, respectively, compared with the unadjusted data) in the percentage of herds exceeding a herd SCC of 400,000 cells/mL. Herd eligibility varied by interpretation scenarios, in particular those incorporating seasonal adjustment. The study provides new perspectives on the effect of data adjustment on herd SCC and of interpretation scenarios on herd eligibility. The results provide an illustrative

Adjusting for radiotelemetry error to improve estimates of habitat use.

Treesearch

Scott L. Findholt; Bruce K. Johnson; Lyman L. McDonald; John W. Kern; Alan Ager; Rosemary J. Stussy; Larry D. Bryant

2002-01-01

Animal locations estimated from radiotelemetry have traditionally been treated as error-free when analyzed in relation to habitat variables. Location error lowers the power of statistical tests of habitat selection. We describe a method that incorporates the error surrounding point estimates into measures of environmental variables determined from a geographic...

Investigating the utility of a GPA institutional adjustment index.

PubMed

Didier, Thomas; Kreiter, Clarence D; Buri, Russell; Solow, Catherine

2006-05-01

Grading standards vary widely across undergraduate institutions. If, during the medical school admissions process, GPA is considered without reference to the institution attended, it will disadvantage applicants from undergraduate institutions employing rigorous grading standards. A regression-based GPA institutional equating method using historical MCAT and GPA information is described. Classes selected from eight applicant pools demonstrate the impact of the GPA adjustment. The validity of the adjustment is examined by comparing adjusted and unadjusted GPAs' correlation with USMLE and medical college grades. The adjusted GPA demonstrated significantly improved congruence with MCAT estimates of applicant preparedness. The adjustment changed selection decisions for 21% of those admitted. The adjusted GPA enhanced prediction of USMLE and medical school grades only for students from institutions which required large adjustments. Unlike other indices, the adjustment described uses the same metric as GPA and is based only on an institution's history of preparing medical school applicants. The institutional adjustment is consequential in selection, significantly enhances congruence with a standardized measure of academic preparedness and may enhance the validity of the GPA.

A demand-side view of risk adjustment.

PubMed

Feldman, R; Dowd, B E; Maciejewski, M

2001-01-01

This paper analyzes the efficient allocation of consumers to health plans. Specifically, we address the question of why employers that offer multiple health plans often make larger contributions to the premiums of the high-cost plans. Our perspective is that the subsidy for high-cost plans represents a form of demand-side risk adjustment that improves efficiency. Without such subsidies (and in the absence of formal risk adjustment), too few employees would choose the high-cost plans preferred by high-risk workers. We test the theory by estimating a model of the employer premium subsidy, using data from a survey of large public employers in 1994. Our empirical analysis shows that employers are more likely to subsidize high-cost plans when the benefits of risk adjustment are greater. The findings suggest that the premium subsidy can accomplish some of the benefits of formal risk adjustment.

Improving observational study estimates of treatment effects using joint modeling of selection effects and outcomes: the case of AAA repair.

PubMed

O'Malley, A James; Cotterill, Philip; Schermerhorn, Marc L; Landon, Bruce E

2011-12-01

When 2 treatment approaches are available, there are likely to be unmeasured confounders that influence choice of procedure, which complicates estimation of the causal effect of treatment on outcomes using observational data. To estimate the effect of endovascular (endo) versus open surgical (open) repair, including possible modification by institutional volume, on survival after treatment for abdominal aortic aneurysm, accounting for observed and unobserved confounding variables. Observational study of data from the Medicare program using a joint model of treatment selection and survival given treatment to estimate the effects of type of surgery and institutional volume on survival. We studied 61,414 eligible repairs of intact abdominal aortic aneurysms during 2001 to 2004. The outcome, perioperative death, is defined as in-hospital death or death within 30 days of operation. The key predictors are use of endo, transformed endo and open volume, and endo-volume interactions. There is strong evidence of nonrandom selection of treatment with potential confounding variables including institutional volume and procedure date, variables not typically adjusted for in clinical trials. The best fitting model included heterogeneous transformations of endo volume for endo cases and open volume for open cases as predictors. Consistent with our hypothesis, accounting for unmeasured selection reduced the mortality benefit of endo. The effect of endo versus open surgery varies nonlinearly with endo and open volume. Accounting for institutional experience and unmeasured selection enables better decision-making by physicians making treatment referrals, investigators evaluating treatments, and policy makers.

Women and Retirement: The Effect of Multiple Careers on Retirement Adjustment.

ERIC Educational Resources Information Center

Connidis, Ingrid

1982-01-01

The concept of career set is employed as the basis for a framework designed to analyze the impact of women's involvement in multiple careers on their adjustment to retirement. The author concludes that the familial careers engaged in by married, working women have a mediative effect on their transition to retirement. (Author/CT)

Residential self-selection bias in the estimation of built environment effects on physical activity between adolescence and young adulthood.

PubMed

Boone-Heinonen, Janne; Guilkey, David K; Evenson, Kelly R; Gordon-Larsen, Penny

2010-10-04

Built environment research is dominated by cross-sectional designs, which are particularly vulnerable to residential self-selection bias resulting from health-related attitudes, neighborhood preferences, or other unmeasured characteristics related to both neighborhood choice and health-related outcomes. We used cohort data from the National Longitudinal Study of Adolescent Health (United States; Wave I, 1994-95; Wave III, 2001-02; n = 12,701) and a time-varying geographic information system. Longitudinal relationships between moderate to vigorous physical activity (MVPA) bouts and built and socioeconomic environment measures (landcover diversity, pay and public physical activity facilities per 10,000 population, street connectivity, median household income, and crime rate) from adolescence to young adulthood were estimated using random effects models (biased by unmeasured confounders) and fixed effects models (within-person estimator, which adjusts for unmeasured confounders that are stable over time). Random effects models yielded null associations except for negative crime-MVPA associations [coefficient (95% CI): -0.056 (-0.083, -0.029) in males, -0.061 (-0.090, -0.033) in females]. After controlling for measured and time invariant unmeasured characteristics using within-person estimators, MVPA was higher with greater physical activity pay facilities in males [coefficient (95% CI): 0.024 (0.006, 0.042)], and lower with higher crime rates in males [coefficient (95% CI): -0.107 (-0.140, -0.075)] and females [coefficient (95% CI): -0.046 (-0.083, -0.009)]. Other associations were null or in the counter-intuitive direction. Comparison of within-person estimates to estimates unadjusted for unmeasured characteristics suggest that residential self-selection can bias associations toward the null, as opposed to its typical characterization as a positive confounder. Differential environment-MVPA associations by residential relocation suggest that studies examining changes

Alcohol effects on performance monitoring and adjustment: affect modulation and impairment of evaluative cognitive control.

PubMed

Bartholow, Bruce D; Henry, Erika A; Lust, Sarah A; Saults, J Scott; Wood, Phillip K

2012-02-01

Alcohol is known to impair self-regulatory control of behavior, though mechanisms for this effect remain unclear. Here, we tested the hypothesis that alcohol's reduction of negative affect (NA) is a key mechanism for such impairment. This hypothesis was tested by measuring the amplitude of the error-related negativity (ERN), a component of the event-related brain potential (ERP) posited to reflect the extent to which behavioral control failures are experienced as distressing, while participants completed a laboratory task requiring self-regulatory control. Alcohol reduced both the ERN and error positivity (Pe) components of the ERP following errors and impaired typical posterror behavioral adjustment. Structural equation modeling indicated that effects of alcohol on both the ERN and posterror adjustment were significantly mediated by reductions in NA. Effects of alcohol on Pe amplitude were unrelated to posterror adjustment, however. These findings indicate a role for affect modulation in understanding alcohol's effects on self-regulatory impairment and more generally support theories linking the ERN with a distress-related response to control failures. PsycINFO Database Record (c) 2012 APA, all rights reserved.

Frequency Estimator Performance for a Software-Based Beacon Receiver

NASA Technical Reports Server (NTRS)

Zemba, Michael J.; Morse, Jacquelynne Rose; Nessel, James A.; Miranda, Felix

2014-01-01

As propagation terminals have evolved, their design has trended more toward a software-based approach that facilitates convenient adjustment and customization of the receiver algorithms. One potential improvement is the implementation of a frequency estimation algorithm, through which the primary frequency component of the received signal can be estimated with a much greater resolution than with a simple peak search of the FFT spectrum. To select an estimator for usage in a QV-band beacon receiver, analysis of six frequency estimators was conducted to characterize their effectiveness as they relate to beacon receiver design.

Frequency Estimator Performance for a Software-Based Beacon Receiver

NASA Technical Reports Server (NTRS)

Zemba, Michael J.; Morse, Jacquelynne R.; Nessel, James A.

2014-01-01

As propagation terminals have evolved, their design has trended more toward a software-based approach that facilitates convenient adjustment and customization of the receiver algorithms. One potential improvement is the implementation of a frequency estimation algorithm, through which the primary frequency component of the received signal can be estimated with a much greater resolution than with a simple peak search of the FFT spectrum. To select an estimator for usage in a Q/V-band beacon receiver, analysis of six frequency estimators was conducted to characterize their effectiveness as they relate to beacon receiver design.

Long-Term Large-Scale Bias-Adjusted Precipitation Estimates at High Spatial and Temporal Resolution Derived from the National Mosaic and Multi-Sensor QPE (NMQ/Q2) Precipitation Reanalysis over CONUS

NASA Astrophysics Data System (ADS)

Prat, O. P.; Nelson, B. R.; Stevens, S. E.; Seo, D. J.; Kim, B.

2014-12-01

The processing of radar-only precipitation via the reanalysis from the National Mosaic and Multi-Sensor Quantitative (NMQ/Q2) based on the WSR-88D Next-generation Radar (Nexrad) network over Continental United States (CONUS) is nearly completed for the period covering from 2000 to 2012. This important milestone constitutes a unique opportunity to study precipitation processes at a 1-km spatial resolution for a 5-min temporal resolution. However, in order to be suitable for hydrological, meteorological and climatological applications, the radar-only product needs to be bias-adjusted and merged with in-situ rain gauge information. Rain gauge networks such as the Hydrometeorological Automated Data System (HADS), the Automated Surface Observing Systems (ASOS), the Climate Reference Network (CRN), and the Global Historical Climatology Network - Daily (GHCN-D) are used to adjust for those biases and to merge with the radar only product to provide a multi-sensor estimate. The challenges related to incorporating non-homogeneous networks over a vast area and for a long-term record are enormous. Among the challenges we are facing are the difficulties incorporating differing resolution and quality surface measurements to adjust gridded estimates of precipitation. Another challenge is the type of adjustment technique. After assessing the bias and applying reduction or elimination techniques, we are investigating the kriging method and its variants such as simple kriging (SK), ordinary kriging (OK), and conditional bias-penalized Kriging (CBPK) among others. In addition we hope to generate estimates of uncertainty for the gridded estimate. In this work the methodology is presented as well as a comparison between the radar-only product and the final multi-sensor QPE product. The comparison is performed at various time scales from the sub-hourly, to annual. In addition, comparisons over the same period with a suite of lower resolution QPEs derived from ground based radar

Recent tobacco tax rate adjustment and its potential impact on tobacco control in China.

PubMed

Hu, Teh-Wei; Mao, Zhengzhong; Shi, Jian

2010-02-01

To compare the new tobacco tax structure effective from May 2009 with the tax structure before May 2009 and to analyse its potential impact. Published government statistics and estimated price elasticities of the demand for cigarettes are used to estimate the impact of the new tax rate adjustment on cigarette consumption and population health. The new adjustment increased the tax rate by 11.7% points at the producer price level. Converting this 11.7% point increase to the retail price level would mean an increase of 3.4% points in the retail price tax rate. Thus, China's new cigarette tax rate at the retail level would be 43.4% instead of the previous 40%. The primary motivation for the recent Chinese government tobacco tax adjustment is to raise additional government revenue. Because the additional ad valorem tax has not yet been transferred to smokers, there is no public health benefit. It is hoped that the Chinese government will pass along these taxes to the retail price level, which would result in between 640,000 and two million smokers quitting smoking and between 210,000 and 700,000 quitters avoiding smoking-related premature death.

Adjustable Autonomy Testbed

NASA Technical Reports Server (NTRS)

Malin, Jane T.; Schrenkenghost, Debra K.

2001-01-01

The Adjustable Autonomy Testbed (AAT) is a simulation-based testbed located in the Intelligent Systems Laboratory in the Automation, Robotics and Simulation Division at NASA Johnson Space Center. The purpose of the testbed is to support evaluation and validation of prototypes of adjustable autonomous agent software for control and fault management for complex systems. The AA T project has developed prototype adjustable autonomous agent software and human interfaces for cooperative fault management. This software builds on current autonomous agent technology by altering the architecture, components and interfaces for effective teamwork between autonomous systems and human experts. Autonomous agents include a planner, flexible executive, low level control and deductive model-based fault isolation. Adjustable autonomy is intended to increase the flexibility and effectiveness of fault management with an autonomous system. The test domain for this work is control of advanced life support systems for habitats for planetary exploration. The CONFIG hybrid discrete event simulation environment provides flexible and dynamically reconfigurable models of the behavior of components and fluids in the life support systems. Both discrete event and continuous (discrete time) simulation are supported, and flows and pressures are computed globally. This provides fast dynamic simulations of interacting hardware systems in closed loops that can be reconfigured during operations scenarios, producing complex cascading effects of operations and failures. Current object-oriented model libraries support modeling of fluid systems, and models have been developed of physico-chemical and biological subsystems for processing advanced life support gases. In FY01, water recovery system models will be developed.

Deep space network software cost estimation model

NASA Technical Reports Server (NTRS)

Tausworthe, R. C.

1981-01-01

A parametric software cost estimation model prepared for Deep Space Network (DSN) Data Systems implementation tasks is presented. The resource estimation model incorporates principles and data from a number of existing models. The model calibrates task magnitude and difficulty, development environment, and software technology effects through prompted responses to a set of approximately 50 questions. Parameters in the model are adjusted to fit DSN software life cycle statistics. The estimation model output scales a standard DSN Work Breakdown Structure skeleton, which is then input into a PERT/CPM system, producing a detailed schedule and resource budget for the project being planned.

Including information about comorbidity in estimates of disease burden: Results from the WHO World Mental Health Surveys

PubMed Central

Alonso, Jordi; Vilagut, Gemma; Chatterji, Somnath; Heeringa, Steven; Schoenbaum, Michael; Üstün, T. Bedirhan; Rojas-Farreras, Sonia; Angermeyer, Matthias; Bromet, Evelyn; Bruffaerts, Ronny; de Girolamo, Giovanni; Gureje, Oye; Haro, Josep Maria; Karam, Aimee N.; Kovess, Viviane; Levinson, Daphna; Liu, Zhaorui; Mora, Maria Elena Medina; Ormel, J.; Posada-Villa, Jose; Uda, Hidenori; Kessler, Ronald C.

2010-01-01

Background The methodology commonly used to estimate disease burden, featuring ratings of severity of individual conditions, has been criticized for ignoring comorbidity. A methodology that addresses this problem is proposed and illustrated here with data from the WHO World Mental Health Surveys. Although the analysis is based on self-reports about one’s own conditions in a community survey, the logic applies equally well to analysis of hypothetical vignettes describing comorbid condition profiles. Methods Face-to-face interviews in 13 countries (six developing, nine developed; n = 31,067; response rate = 69.6%) assessed 10 classes of chronic physical and 9 of mental conditions. A visual analog scale (VAS) was used to assess overall perceived health. Multiple regression analysis with interactions for comorbidity was used to estimate associations of conditions with VAS. Simulation was used to estimate condition-specific effects. Results The best-fitting model included condition main effects and interactions of types by numbers of conditions. Neurological conditions, insomnia, and major depression were rated most severe. Adjustment for comorbidity reduced condition-specific estimates with substantial between-condition variation (.24–.70 ratios of condition-specific estimates with and without adjustment for comorbidity). The societal-level burden rankings were quite different from the individual-level rankings, with the highest societal-level rankings associated with conditions having high prevalence rather than high individual-level severity. Conclusions Plausible estimates of disorder-specific effects on VAS can be obtained using methods that adjust for comorbidity. These adjustments substantially influence condition-specific ratings. PMID:20553636

Lung cancer among coal miners, ore miners and quarrymen: smoking-adjusted risk estimates from the synergy pooled analysis of case-control studies.

PubMed

Taeger, Dirk; Pesch, Beate; Kendzia, Benjamin; Behrens, Thomas; Jöckel, Karl-Heinz; Dahmann, Dirk; Siemiatycki, Jack; Kromhout, Hans; Vermeulen, Roel; Peters, Susan; Olsson, Ann; Brüske, Irene; Wichmann, Heinz-Erich; Stücker, Isabelle; Guida, Florence; Tardón, Adonina; Merletti, Franco; Mirabelli, Dario; Richiardi, Lorenzo; Pohlabeln, Hermann; Ahrens, Wolfgang; Landi, Maria Teresa; Caporaso, Neil; Pesatori, Angela Cecilia; Mukeriya, Anush; Szeszenia-Dabrowska, Neonila; Lissowska, Jolanta; Gustavsson, Per; Field, John; Marcus, Michael W; Fabianova, Eleonora; 't Mannetje, Andrea; Pearce, Neil; Rudnai, Peter; Bencko, Vladimir; Janout, Vladimir; Dumitru, Rodica Stanescu; Foretova, Lenka; Forastiere, Francesco; McLaughlin, John; Paul Demers, Paul Demers; Bueno-de-Mesquita, Bas; Schüz, Joachim; Straif, Kurt; Brüning, Thomas

2015-09-01

Working in mines and quarries has been associated with an elevated lung cancer risk but with inconsistent results for coal miners. This study aimed to estimate the smoking-adjusted lung cancer risk among coal miners and compare the risk pattern with lung cancer risks among ore miners and quarrymen. We estimated lung cancer risks of coal and ore miners and quarrymen among 14 251 lung cancer cases and 17 267 controls from the SYNERGY pooled case-control study, controlling for smoking and employment in other at-risk occupations. Ever working as miner or quarryman (690 cases, 436 controls) was associated with an elevated odds ratio (OR) of 1.55 [95% confidence interval (95% CI) 1.34-1.79] for lung cancer. Ore miners (53 cases, 24 controls) had a higher OR (2.34, 95% CI 1.36-4.03) than quarrymen (67 cases, 39 controls; OR 1.92, 95% CI 1.21-3.05) and coal miners (442 cases, 297 controls; OR 1.40, 95% CI 1.18-1.67), but CI overlapped. We did not observe trends by duration of exposure or time since last exposure. This pooled analysis of population-based studies demonstrated an excess lung cancer risk among miners and quarrymen that remained increased after adjustment for detailed smoking history and working in other at-risk occupations. The increase in risk among coal miners were less pronounced than for ore miners or quarrymen.

The Fifth Cell: Correlation Bias in U.S. Census Adjustment.

ERIC Educational Resources Information Center

Wachter, Kenneth W.; Freedman, David A.

2000-01-01

Presents a method for estimating the total national number of doubly missing people (missing from Census counts and adjusted counts as well) and their distribution by race and sex. Application to the 1990 U.S. Census yields an estimate of three million doubly-missing people. (SLD)

The effects of muscle vibration on anticipatory postural adjustments.

PubMed

Slijper, Harm; Latash, Mark L

2004-07-23

The current study investigated the influence of changes in sensory information related to postural stability on anticipatory postural adjustments (APAs) in standing subjects. Subjects performed fast arm movements and a load release task while standing on a stable force platform or on an unstable board. We manipulated sensory information through vibration of the Achilles tendons and additional finger touch (contact forces under 1 N). Changes in the background activity of leg, trunk, and arm muscles and displacements of the center of pressure (COP) were quantified within time intervals typical for APAs. In the arm movement task, leg and trunk muscles showed a significant drop in the APAs with finger touch, while the vibration and standing on the unstable board each led to an increase in the APA magnitude. In the load release task, ventral muscles decreased their APA activity with touch, while dorsal muscles showed increased inhibition during APAs. During vibration, dorsal and ventral muscles showed increased excitation and inhibition during APAs, respectively. An additional analysis of APAs at a joint level, has shown that in both tasks, an index related to the co-activation of agonist-antagonist muscle pairs (C-index) was modulated with touch, vibration, and stability particularly in leg muscles. Small changes in the other index related to reciprocal activation (R-index) were found only in trunk muscles. Light touch and vibration induced opposing changes in the C-index, suggesting their opposite effects on the stabilization of a reference point or vertical. We conclude that the central nervous system deploys patterns of adjustments in which increased co-contraction of distal muscles and reciprocal adjustments in trunk muscles are modified to ensure equilibrium under postural instability.

Treatment Effect Estimation Using Nonlinear Two-Stage Instrumental Variable Estimators: Another Cautionary Note.

PubMed

Chapman, Cole G; Brooks, John M

2016-12-01

To examine the settings of simulation evidence supporting use of nonlinear two-stage residual inclusion (2SRI) instrumental variable (IV) methods for estimating average treatment effects (ATE) using observational data and investigate potential bias of 2SRI across alternative scenarios of essential heterogeneity and uniqueness of marginal patients. Potential bias of linear and nonlinear IV methods for ATE and local average treatment effects (LATE) is assessed using simulation models with a binary outcome and binary endogenous treatment across settings varying by the relationship between treatment effectiveness and treatment choice. Results show that nonlinear 2SRI models produce estimates of ATE and LATE that are substantially biased when the relationships between treatment and outcome for marginal patients are unique from relationships for the full population. Bias of linear IV estimates for LATE was low across all scenarios. Researchers are increasingly opting for nonlinear 2SRI to estimate treatment effects in models with binary and otherwise inherently nonlinear dependent variables, believing that it produces generally unbiased and consistent estimates. This research shows that positive properties of nonlinear 2SRI rely on assumptions about the relationships between treatment effect heterogeneity and choice. © Health Research and Educational Trust.

Indirect medical education and disproportionate share adjustments to Medicare inpatient payment rates.

PubMed

Nguyen, Nguyen Xuan; Sheingold, Steven H

2011-11-04

The indirect medical education (IME) and disproportionate share hospital (DSH) adjustments to Medicare's prospective payment rates for inpatient services are generally intended to compensate hospitals for patient care costs related to teaching activities and care of low income populations. These adjustments were originally established based on the statistical relationships between IME and DSH and hospital costs. Due to a variety of policy considerations, the legislated levels of these adjustments may have deviated over time from these "empirically justified levels," or simply, "empirical levels." In this paper, we estimate the empirical levels of IME and DSH using 2006 hospital data and 2009 Medicare final payment rules. Our analyses suggest that the empirical level for IME would be much smaller than under current law-about one-third to one-half. Our analyses also support the DSH adjustment prescribed by the Affordable Care Act of 2010 (ACA)--about one-quarter of the pre-ACA level. For IME, the estimates imply an increase in costs of 1.88% for each 10% increase in teaching intensity. For DSH, the estimates imply that costs would rise by 0.52% for each 10% increase in the low-income patient share for large urban hospitals. Public Domain.

Advance market commitments for vaccines against neglected diseases: estimating costs and effectiveness.

PubMed

Berndt, Ernst R; Glennerster, Rachel; Kremer, Michael R; Lee, Jean; Levine, Ruth; Weizsäcker, Georg; Williams, Heidi

2007-05-01

The G8 is considering committing to purchase vaccines against diseases concentrated in low-income countries (if and when desirable vaccines are developed) as a way to spur research and development on vaccines for these diseases. Under such an 'advance market commitment,' one or more sponsors would commit to a minimum price to be paid per person immunized for an eligible product, up to a certain number of individuals immunized. For additional purchases, the price would eventually drop to close to marginal cost. If no suitable product were developed, no payments would be made. We estimate the offer size which would make revenues similar to the revenues realized from investments in typical existing commercial pharmaceutical products, as well as the degree to which various model contracts and assumptions would affect the cost-effectiveness of such a commitment. We make adjustments for lower marketing costs under an advance market commitment and the risk that a developer may have to share the market with subsequent developers. We also show how this second risk could be reduced, and money saved, by introducing a superiority clause to a commitment. Under conservative assumptions, we document that a commitment comparable in value to sales earned by the average of a sample of recently launched commercial products (adjusted for lower marketing costs) would be a highly cost-effective way to address HIV/AIDS, malaria, and tuberculosis. Sensitivity analyses suggest most characteristics of a hypothetical vaccine would have little effect on the cost-effectiveness, but that the duration of protection conferred by a vaccine strongly affects potential cost-effectiveness. Readers can conduct their own sensitivity analyses employing a web-based spreadsheet tool. Copyright (c) 2006 John Wiley & Sons, Ltd.

Case mix adjusted nursing-home reimbursement: a critical review of the evidence.

PubMed

Weissert, W G; Musliner, M C

1992-01-01

Nursing-home case mix adjusted payment systems typically base payments on estimates of patients' care needs, but to date the data on their effectiveness are ambiguous. Studies mainly show that access for patients most in need of care appears to improve under these systems. Case mix based payment systems have both positive and negative effects on quality of care and require compensating mechanisms for the potentially harmful incentives they can generate. On the positive side, nursing homes are paid more equitably; the negative aspect is reflected in higher costs, particularly for administration. A Health Care Financing Administration (HCFA) demonstration project may provide insights, but its limited number of predominantly small, rural, participating states, its tandem quality assurance system, and potentially confounding market variables may restrict the value of this project. We do not yet have the data to assess the impact of instituting case mix adjustment systems.

The necessity of sociodemographic status adjustment in hospital value rankings for perforated appendicitis in children.

PubMed

Tian, Yao; Sweeney, John F; Wulkan, Mark L; Heiss, Kurt F; Raval, Mehul V

2016-06-01

Hospitals are increasingly focused on demonstration of high-value care for common surgical procedures. Although sociodemographic status (SDS) factors have been tied to various surgical outcomes, the impact of SDS factors on hospital value rankings has not been well explored. Our objective was to examine effects of SDS factors on high-value surgical care at the patient level, and to illustrate the importance of SDS adjustment when evaluating hospital-level performance. Perforated appendicitis hospitalizations were identified from the 2012 Kids' Inpatient Database. The primary outcome of interest was high-value care as defined by evaluation of duration of stay and cost. SDS factors included race, health insurance type, median household income, and patient location. The impact of SDS on high-value care was estimated using regression models after accounting for hospital-level variation. Risk-adjusted value rankings were compared before and after adjustment for SDS. From 9,986 hospitalizations, 998 high-value encounters were identified. African Americans were less likely to experience high-value care compared with white patients after adjusting for all SDS variables. Although private insurance and living in nonmetro counties were associated independently with high-value care, the effects were attenuated in the fully adjusted models. For the 136 hospitals ranked according to risk-adjusted value status, 59 hospitals' rankings improved after adjustment and 53 hospitals' rankings declined. After adjustment for patient and hospital factors, SDS has a small but significant impact on risk-adjusted hospital performance ranking for pediatric appendicitis. Adjustment for SDS should be considered in future comparative performance assessment. Copyright © 2016 Elsevier Inc. All rights reserved.

Semi-Global Matching with Self-Adjusting Penalties

NASA Astrophysics Data System (ADS)

Karkalou, E.; Stentoumis, C.; Karras, G.

2017-02-01

The demand for 3D models of various scales and precisions is strong for a wide range of applications, among which cultural heritage recording is particularly important and challenging. In this context, dense image matching is a fundamental task for processes which involve image-based reconstruction of 3D models. Despite the existence of commercial software, the need for complete and accurate results under different conditions, as well as for computational efficiency under a variety of hardware, has kept image-matching algorithms as one of the most active research topics. Semi-global matching (SGM) is among the most popular optimization algorithms due to its accuracy, computational efficiency, and simplicity. A challenging aspect in SGM implementation is the determination of smoothness constraints, i.e. penalties P1, P2 for disparity changes and discontinuities. In fact, penalty adjustment is needed for every particular stereo-pair and cost computation. In this work, a novel formulation of self-adjusting penalties is proposed: SGM penalties can be estimated solely from the statistical properties of the initial disparity space image. The proposed method of self-adjusting penalties (SGM-SAP) is evaluated using typical cost functions on stereo-pairs from the recent Middlebury dataset of interior scenes, as well as from the EPFL Herz-Jesu architectural scenes. Results are competitive against the original SGM estimates. The significant aspects of self-adjusting penalties are: (i) the time-consuming tuning process is avoided; (ii) SGM can be used in image collections with limited number of stereo-pairs; and (iii) no heuristic user intervention is needed.

Refined estimates of local recurrence risks by DCIS score adjusting for clinicopathological features: a combined analysis of ECOG-ACRIN E5194 and Ontario DCIS cohort studies.

PubMed

Rakovitch, E; Gray, R; Baehner, F L; Sutradhar, R; Crager, M; Gu, S; Nofech-Mozes, S; Badve, S S; Hanna, W; Hughes, L L; Wood, W C; Davidson, N E; Paszat, L; Shak, S; Sparano, J A; Solin, L J

2018-06-01

Better tools are needed to estimate local recurrence (LR) risk after breast-conserving surgery (BCS) for DCIS. The DCIS score (DS) was validated as a predictor of LR in E5194 and Ontario DCIS cohort (ODC) after BCS. We combined data from E5194 and ODC adjusting for clinicopathological factors to provide refined estimates of the 10-year risk of LR after treatment by BCS alone. Data from E5194 and ODC were combined. Patients with positive margins or multifocality were excluded. Identical Cox regression models were fit for each study. Patient-specific meta-analysis was used to calculate precision-weighted estimates of 10-year LR risk by DS, age, tumor size and year of diagnosis. The combined cohort includes 773 patients. The DS and age at diagnosis, tumor size and year of diagnosis provided independent prognostic information on the 10-year LR risk (p ≤ 0.009). Hazard ratios from E5194 and ODC cohorts were similar for the DS (2.48, 1.95 per 50 units), tumor size ≤ 1 versus  > 1-2.5 cm (1.45, 1.47), age ≥ 50 versus < 50 year (0.61, 0.84) and year ≥ 2000 (0.67, 0.49). Utilization of DS combined with tumor size and age at diagnosis predicted more women with very low (≤ 8%) or higher (> 15%) 10-year LR risk after BCS alone compared to utilization of DS alone or clinicopathological factors alone. The combined analysis provides refined estimates of 10-year LR risk after BCS for DCIS. Adding information on tumor size and age at diagnosis to the DS adjusting for year of diagnosis provides improved LR risk estimates to guide treatment decision making.

Aging effect on step adjustments and stability control in visually perturbed gait initiation.

PubMed

Sun, Ruopeng; Cui, Chuyi; Shea, John B

2017-10-01

Gait adaptability is essential for fall avoidance during locomotion. It requires the ability to rapidly inhibit original motor planning, select and execute alternative motor commands, while also maintaining the stability of locomotion. This study investigated the aging effect on gait adaptability and dynamic stability control during a visually perturbed gait initiation task. A novel approach was used such that the anticipatory postural adjustment (APA) during gait initiation were used to trigger the unpredictable relocation of a foot-size stepping target. Participants (10 young adults and 10 older adults) completed visually perturbed gait initiation in three adjustment timing conditions (early, intermediate, late; all extracted from the stereotypical APA pattern) and two adjustment direction conditions (medial, lateral). Stepping accuracy, foot rotation at landing, and Margin of Dynamic Stability (MDS) were analyzed and compared across test conditions and groups using a linear mixed model. Stepping accuracy decreased as a function of adjustment timing as well as stepping direction, with older subjects exhibited a significantly greater undershoot in foot placement to late lateral stepping. Late adjustment also elicited a reaching-like movement (i.e. foot rotation prior to landing in order to step on the target), regardless of stepping direction. MDS measures in the medial-lateral and anterior-posterior direction revealed both young and older adults exhibited reduced stability in the adjustment step and subsequent steps. However, young adults returned to stable gait faster than older adults. These findings could be useful for future study of screening deficits in gait adaptability and preventing falls. Copyright © 2017 Elsevier B.V. All rights reserved.

Estimating the Cost-Effectiveness of HIV Prevention Programmes in Vietnam, 2006-2010: A Modelling Study

PubMed Central

Pham, Quang Duy; Wilson, David P.; Kerr, Cliff C.; Shattock, Andrew J.; Do, Hoa Mai; Duong, Anh Thuy; Nguyen, Long Thanh; Zhang, Lei

2015-01-01

Introduction Vietnam has been largely reliant on international support in its HIV response. Over 2006-2010, a total of US$480 million was invested in its HIV programmes, more than 70% of which came from international sources. This study investigates the potential epidemiological impacts of these programmes and their cost-effectiveness. Methods We conducted a data synthesis of HIV programming, spending, epidemiological, and clinical outcomes. Counterfactual scenarios were defined based on assumed programme coverage and behaviours had the programmes not been implemented. An epidemiological model, calibrated to reflect the actual epidemiological trends, was used to estimate plausible ranges of programme impacts. The model was then used to estimate the costs per averted infection, death, and disability adjusted life-year (DALY). Results Based on observed prevalence reductions amongst most population groups, and plausible counterfactuals, modelling suggested that antiretroviral therapy (ART) and prevention programmes over 2006-2010 have averted an estimated 50,600 [95% uncertainty bound: 36,300–68,900] new infections and 42,600 [36,100–54,100] deaths, resulting in 401,600 [312,200–496,300] fewer DALYs across all population groups. HIV programmes in Vietnam have cost an estimated US$1,972 [1,447–2,747], US$2,344 [1,843–2,765], and US$248 [201–319] for each averted infection, death, and DALY, respectively. Conclusions Our evaluation suggests that HIV programmes in Vietnam have most likely had benefits that are cost-effective. ART and direct HIV prevention were the most cost-effective interventions in reducing HIV disease burden. PMID:26196290

Environmental Chemicals in Urine and Blood: Improving Methods for Creatinine and Lipid Adjustment

PubMed Central

O’Brien, Katie M.; Upson, Kristen; Cook, Nancy R.; Weinberg, Clarice R.

2015-01-01

Background Investigators measuring exposure biomarkers in urine typically adjust for creatinine to account for dilution-dependent sample variation in urine concentrations. Similarly, it is standard to adjust for serum lipids when measuring lipophilic chemicals in serum. However, there is controversy regarding the best approach, and existing methods may not effectively correct for measurement error. Objectives We compared adjustment methods, including novel approaches, using simulated case–control data. Methods Using a directed acyclic graph framework, we defined six causal scenarios for epidemiologic studies of environmental chemicals measured in urine or serum. The scenarios include variables known to influence creatinine (e.g., age and hydration) or serum lipid levels (e.g., body mass index and recent fat intake). Over a range of true effect sizes, we analyzed each scenario using seven adjustment approaches and estimated the corresponding bias and confidence interval coverage across 1,000 simulated studies. Results For urinary biomarker measurements, our novel method, which incorporates both covariate-adjusted standardization and the inclusion of creatinine as a covariate in the regression model, had low bias and possessed 95% confidence interval coverage of nearly 95% for most simulated scenarios. For serum biomarker measurements, a similar approach involving standardization plus serum lipid level adjustment generally performed well. Conclusions To control measurement error bias caused by variations in serum lipids or by urinary diluteness, we recommend improved methods for standardizing exposure concentrations across individuals. Citation O’Brien KM, Upson K, Cook NR, Weinberg CR. 2016. Environmental chemicals in urine and blood: improving methods for creatinine and lipid adjustment. Environ Health Perspect 124:220–227; http://dx.doi.org/10.1289/ehp.1509693 PMID:26219104

Three estimates of the association between linear growth failure and cognitive ability.

PubMed

Cheung, Y B; Lam, K F

2009-09-01

To compare three estimators of association between growth stunting as measured by height-for-age Z-score and cognitive ability in children, and to examine the extent statistical adjustment for covariates is useful for removing confounding due to socio-economic status. Three estimators, namely random-effects, within- and between-cluster estimators, for panel data were used to estimate the association in a survey of 1105 pairs of siblings who were assessed for anthropometry and cognition. Furthermore, a 'combined' model was formulated to simultaneously provide the within- and between-cluster estimates. Random-effects and between-cluster estimators showed strong association between linear growth and cognitive ability, even after adjustment for a range of socio-economic variables. In contrast, the within-cluster estimator showed a much more modest association: For every increase of one Z-score in linear growth, cognitive ability increased by about 0.08 standard deviation (P < 0.001). The combined model verified that the between-cluster estimate was significantly larger than the within-cluster estimate (P = 0.004). Residual confounding by socio-economic situations may explain a substantial proportion of the observed association between linear growth and cognition in studies that attempt to control the confounding by means of multivariable regression analysis. The within-cluster estimator provides more convincing and modest results about the strength of association.

Effects of diet form and feeder adjustment on growth performance of nursery and finishing pigs.

PubMed

Nemechek, J E; Tokach, M D; Dritz, S S; Fruge, E D; Hansen, E L; Goodband, R D; DeRouchey, J M; Woodworth, J C

2015-08-01

Three experiments were conducted to determine the effects of feeder adjustment and diet form on growth performance of nursery (Exp. 1 and 2) and finishing (Exp. 3) pigs. Treatments were arranged as a 2 × 3 factorial with the main effects of feeder adjustment and diet form. The 2 feeder adjustments were a narrow and wide feeder adjustment (minimum gap opening of 1.27 and 2.54 cm, respectively). The 3 diet forms were meal, poor-quality pellets (70% pellets and 30% fines for Exp. 1 and 2 and 50% pellets and 50% fines for Exp. 3), and screened pellets with minimal fines (3 to 10%). In Exp. 1, 210 pigs (initially 11.9 kg BW) were used in a 21-d trial with 7 pigs per pen and 5 pens per treatment. No feeder adjustment × diet form interactions were observed. There were no differences in ADG, ADFI, or G:F due to feeder adjustment. Pigs fed the meal diet had increased ( < 0.05) ADG and ADFI compared with pigs fed the poor-quality or screened pellets. Pigs fed meal or poor-quality pellets had decreased ( < 0.05) G:F compared with pigs fed screened pellets. In Exp. 2, 1,005 nursery pigs (initially 14.1 kg BW) were used in a 28-d trial with 26 to 28 pigs per pen and 6 pens per treatment. Pigs fed from the narrow feeder adjustment had decreased ( < 0.05) ADG and ADFI compared with pigs fed from the wide adjustment with no differences in G:F. Pigs fed the meal diet had decreased ( < 0.05) ADG compared with pigs fed poor-quality or screened pellets. Pigs fed meal or poor-quality pellets had decreased ( < 0.05) G:F compared with pigs fed screened pellets. In Exp. 3, 246 pigs (initially 56.8 kg BW) were used in a 69-d trial with 5 pens per treatment and 6 or 7 pigs per pen. Overall, ADFI decreased ( < 0.05) and G:F increased ( < 0.05) for pigs fed from the narrow adjusted feeders compared with the wide adjustment with no differences in ADG. Overall, pigs fed meal diets tended to have decreased ( < 0.10) ADG and had decreased ( < 0.05) G:F compared with pigs fed screened pellets

Posttraumatic growth moderates the effects of posttraumatic stress symptoms on adjustment and positive affective reactions in digestive system cancer patients.

PubMed

Ben-Zur, Hasida; Cohen, Miri; Gouzman, Julia

2015-01-01

The study aims were twofold: (1) To investigate the associations of posttraumatic stress symptoms (PTSS) and posttraumatic growth (PTG) with adjustment and affective reactions of digestive system cancer patients and (2) To assess the moderating effects of PTG on the associations of PTSS with adjustment and affective reactions. The sample consisted of 200 respondents 1-4 years following diagnosis and treatment for digestive system cancer. Participants completed questionnaires assessing PTSS, PTG, adjustment, positive affect (PA), and negative affect (NA). The results showed that PTG was positively associated with adjustment and PA, while PTSS was negatively associated with these outcomes and positively associated with NA. Moderation effects of PTG were also observed: The negative associations between PTSS and adjustment or PA were weaker under high levels than under low levels of PTG. It was concluded that PTG is important both as a contributor to better adjustment and PA, as well as a moderator of the detrimental effects of PTSS on adjustment and PA following recovery from cancer. Thus, when developing post-cancer intervention programs, PTG should be viewed as a factor to be encouraged and nurtured for the benefit of cancer patients' adjustment and their long-term well-being.

19 CFR 351.413 - Disregarding insignificant adjustments.

Code of Federal Regulations, 2010 CFR

2010-04-01

... any group of adjustments having an ad valorem effect of less than 1.0 percent, of the export price, constructed export price, or normal value, as the case may be. Groups of adjustments are adjustments for differences in circumstances of sale under § 351.410, adjustments for differences in the physical...

Ethnicity moderates the effects of resources on adjustment of Jewish and Arab mothers of children diagnosed with cancer.

PubMed

Ben-Zur, Hasida; Khoury, Siwar Makhoul

2017-01-01

The study aimed to explore the adjustment of Jewish and Arab mothers of children diagnosed with cancer. Ninety-seven Jewish and 100 Arab mothers completed questionnaires assessing mastery, social support, and adjustment (psychological distress, quality of life, and future fears and hopes). Arab mothers were higher than Jewish mothers on distress and lower on social support and future hopes). Mastery and social support contributed independently to adjustment indices. Ethnicity moderated the effects of mastery and social support on adjustment. Ethnicity, mastery, and social support are important factors in mothers' adjustment to their child's cancer.

Surface term effects on mass estimators

NASA Astrophysics Data System (ADS)

Membrado, M.; Pacheco, A. F.

2016-05-01

Context. We propose a way of estimating the mass contained in the volume occupied by a sample of galaxies in a virialized system. Aims: We analyze the influence of surface effects and the contribution of the cosmological constant terms on our mass estimations of galaxy systems. Methods: We propose two equations that contain surface terms to estimate galaxy sample masses. When the surface terms are neglected, these equations provide the so-called virial and projected masses. Both equations lead to a single equation that allows sample masses to be estimated without the need for calculating surface terms. Sample masses for some nearest galaxy groups are estimated and compared with virialized masses determined from turn-around radii and results of a spherical infall model. Results: Surface effects have a considerable effect on the mass estimations of the studied galaxy groups. According to our results, they lead sample masses of some groups to being less than half the virial mass estimations and even less than 10% of projected mass estimations. However, the contributions of cosmological constant terms to mass estimations are smaller than 2% for the majority of the virialized groups studied. Our estimations are in agreement with virialized masses calculated from turn-around radii. Virialized masses for complexes were found to be: (8.9 ± 2.8) × 1011 M⊙ for the Milky Way - M 31; (12.5 ± 2.5) × 1011 M⊙ for M 81 - NGC 2403; (21.5 ± 7.7) × 1011 M⊙. for Cantaurs A - M 83; and (7.9 ± 2.6) × 1011 M⊙. for IC 324 - Maffei. Conclusions: The nearest galaxy groups located inside a sphere of 5 Mpc have been addressed to explore the performance of our mass estimator. We have seen that surface effects make mass estimations of galaxy groups rather smaller than both virial and projected masses. In mass calculations, cosmological constant terms can be neglected; nevertheless, the collapse of cold dark matter leading to virialized structures is strongly affected by the

Electronic gaming and psychosocial adjustment.

PubMed

Przybylski, Andrew K

2014-09-01

The rise of electronic games has driven both concerns and hopes regarding their potential to influence young people. Existing research identifies a series of isolated positive and negative effects, yet no research to date has examined the balance of these potential effects in a representative sample of children and adolescents. The objective of this study was to explore how time spent playing electronic games accounts for significant variation in positive and negative psychosocial adjustment using a representative cohort of children aged 10 to 15 years. A large sample of children and adolescents aged 10 to 15 years completed assessments of psychosocial adjustment and reported typical daily hours spent playing electronic games. Relations between different levels of engagement and indicators of positive and negative psychosocial adjustment were examined, controlling for participant age and gender and weighted for population representativeness. Low levels (<1 hour daily) as well as high levels (>3 hours daily) of game engagement was linked to key indicators of psychosocial adjustment. Low engagement was associated with higher life satisfaction and prosocial behavior and lower externalizing and internalizing problems, whereas the opposite was found for high levels of play. No effects were observed for moderate play levels when compared with non-players. The links between different levels of electronic game engagement and psychosocial adjustment were small (<1.6% of variance) yet statistically significant. Games consistently but not robustly associated with children's adjustment in both positive and negative ways, findings that inform policy-making as well as future avenues for research in the area. Copyright © 2014 by the American Academy of Pediatrics.

Effects of Systematic Group Counseling on Work Adjustment Clients

ERIC Educational Resources Information Center

Roessler, Richard; And Others

1977-01-01

When compared with a group of clients who had received work adjustment services and a placebo treatment (personal hygiene training), experimental clients given Personal Achievement Skills (PAS) and work adjustment services reported greater gains on self-ratings of life perspective (optimism), work-related attitudes, and goal attainment. (Author)

Exploring methods for comparing the real-world effectiveness of treatments for osteoporosis: adjusted direct comparisons versus using patients as their own control.

PubMed

Karlsson, Linda; Mesterton, Johan; Tepie, Maurille Feudjo; Intorcia, Michele; Overbeek, Jetty; Ström, Oskar

2017-09-21

Using Swedish and Dutch registry data for women initiating bisphosphonates, we evaluated two methods of comparing the real-world effectiveness of osteoporosis treatments that attempt to adjust for differences in patient baseline characteristics. Each method has advantages and disadvantages; both are potential complements to clinical trial analyses. We evaluated methods of comparing the real-world effectiveness of osteoporosis treatments that attempt to adjust for both observed and unobserved confounding. Swedish and Dutch registry data for women initiating zoledronate or oral bisphosphonates (OBPs; alendronate/risedronate) were used; the primary outcome was fracture. In adjusted direct comparisons (ADCs), regression and matching techniques were used to account for baseline differences in known risk factors for fracture (e.g., age, previous fracture, comorbidities). In an own-control analysis (OCA), for each treatment, fracture incidence in the first 90 days following treatment initiation (the baseline risk period) was compared with fracture incidence in the 1-year period starting 91 days after treatment initiation (the treatment exposure period). In total, 1196 and 149 women initiating zoledronate and 14,764 and 25,058 initiating OBPs were eligible in the Swedish and Dutch registries, respectively. Owing to the small Dutch zoledronate sample, only the Swedish data were used to compare fracture incidences between treatment groups. ADCs showed a numerically higher fracture incidence in the zoledronate than in the OBPs group (hazard ratio 1.09-1.21; not statistically significant, p > 0.05). For both treatment groups, OCA showed a higher fracture incidence in the baseline risk period than in the treatment exposure period, indicating a treatment effect. OCA showed a similar or greater effect in the zoledronate group compared with the OBPs group. ADC and OCA each possesses advantages and disadvantages. Combining both methods may provide an estimate of real

Siblings exposed to intimate partner violence: linking sibling relationship quality & child adjustment problems.

PubMed

Piotrowski, Caroline C; Tailor, Ketan; Cormier, Damien C

2014-01-01

Although the majority of families that experience intimate partner violence (IPV) have more than one child, most research to date has focused upon a single child within these families. A significant body of research has indicated siblings play an important role in children's adjustment and well-being. To address this gap, the three main goals of the present study were to compare the adjustment of older and younger siblings exposed to IPV, to describe and compare the quality of these sibling relationships from multiple perspectives, and to investigate how sibling adjustment and relationship quality influence children's adjustment. Forty-seven sibling pairs and their mothers were recruited from the community. Mothers self-reported on their violent experiences using the Conflict Tactics Scale, and also estimated the length of time their children were exposed to IPV. Mothers and children completed assessments of child adjustment and the quality of sibling relationships. Observers also assessed the quality of sibling interaction. Results indicated that adjustment between siblings was highly inter-related. On average, mothers reported sibling relationships as less positive but also as less hostile than did siblings themselves. Higher levels of sibling hostility, lower levels of sibling warmth and higher levels of disengagement each significantly predicted child adjustment; however, these effects were predicated upon the adjustment of the other sibling. The sibling relationships of children exposed to IPV made a difference in their individual adjustment, and their adjustment issues influenced how they feel about and interacted with their sibling. Sibling hostility played a stronger role in adjustment issues than sibling warmth. The nature of sibling influences and the direction of future research were discussed. Copyright © 2013 Elsevier Ltd. All rights reserved.

Intraclass correlation estimates for cancer screening outcomes: estimates and applications in the design of group-randomized cancer screening studies.

PubMed

Hade, Erinn M; Murray, David M; Pennell, Michael L; Rhoda, Dale; Paskett, Electra D; Champion, Victoria L; Crabtree, Benjamin F; Dietrich, Allen; Dignan, Mark B; Farmer, Melissa; Fenton, Joshua J; Flocke, Susan; Hiatt, Robert A; Hudson, Shawna V; Mitchell, Michael; Monahan, Patrick; Shariff-Marco, Salma; Slone, Stacey L; Stange, Kurt; Stewart, Susan L; Strickland, Pamela A Ohman

2010-01-01

Screening has become one of our best tools for early detection and prevention of cancer. The group-randomized trial is the most rigorous experimental design for evaluating multilevel interventions. However, identifying the proper sample size for a group-randomized trial requires reliable estimates of intraclass correlation (ICC) for screening outcomes, which are not available to researchers. We present crude and adjusted ICC estimates for cancer screening outcomes for various levels of aggregation (physician, clinic, and county) and provide an example of how these ICC estimates may be used in the design of a future trial. Investigators working in the area of cancer screening were contacted and asked to provide crude and adjusted ICC estimates using the analysis of variance method estimator. Of the 29 investigators identified, estimates were obtained from 10 investigators who had relevant data. ICC estimates were calculated from 13 different studies, with more than half of the studies collecting information on colorectal screening. In the majority of cases, ICC estimates could be adjusted for age, education, and other demographic characteristics, leading to a reduction in the ICC. ICC estimates varied considerably by cancer site and level of aggregation of the groups. Previously, only two articles had published ICCs for cancer screening outcomes. We have complied more than 130 crude and adjusted ICC estimates covering breast, cervical, colon, and prostate screening and have detailed them by level of aggregation, screening measure, and study characteristics. We have also demonstrated their use in planning a future trial and the need for the evaluation of the proposed interval estimator for binary outcomes under conditions typically seen in GRTs.

Simulation-based estimates of effectiveness and cost-effectiveness of smoking cessation in patients with chronic obstructive pulmonary disease.

PubMed

Atsou, Kokuvi; Chouaid, Christos; Hejblum, Gilles

2011-01-01

The medico-economic impact of smoking cessation considering a smoking patient with chronic obstructive pulmonary disease (COPD) is poorly documented. Here, considering a COPD smoking patient, the specific burden of continuous smoking was estimated, as well as the effectiveness and the cost-effectiveness of smoking cessation. A multi-state Markov model adopting society's perspective was developed. Simulated cohorts of English COPD patients who are active smokers (all severity stages combined or patients with the same initial severity stage) were compared to identical cohorts of patients who quit smoking at cohort initialization. Life expectancy, quality adjusted life-years (QALY), disease-related costs, and incremental cost-effectiveness ratio (ICER: £/QALY) were estimated, considering smoking cessation programs with various possible scenarios of success rates and costs. Sensitivity analyses included the variation of model key parameters. At the horizon of a smoking COPD patient's remaining lifetime, smoking cessation at cohort intitialization, relapses being allowed as observed in practice, would result in gains (mean) of 1.27 life-years and 0.68 QALY, and induce savings of -1824 £/patient in the disease-related costs. The corresponding ICER was -2686 £/QALY. Smoking cessation resulted in 0.72, 0.69, 0.64 and 0.42 QALY respectively gained per mild, moderate, severe, and very severe COPD patient, but was nevertheless cost-effective for mild to severe COPD patients in most scenarios, even when hypothesizing expensive smoking cessation intervention programmes associated with low success rates. Considering a ten-year time horizon, the burden of continuous smoking in English COPD patients was estimated to cost a total of 1657 M£ while 452516 QALY would be simultaneously lost. The study results are a useful support for the setting of smoking cessation programmes specifically targeted to COPD patients.

Adjusting lidar-derived digital terrain models in coastal marshes based on estimated aboveground biomass density

DOE PAGES

Medeiros, Stephen; Hagen, Scott; Weishampel, John; ...

2015-03-25

Digital elevation models (DEMs) derived from airborne lidar are traditionally unreliable in coastal salt marshes due to the inability of the laser to penetrate the dense grasses and reach the underlying soil. To that end, we present a novel processing methodology that uses ASTER Band 2 (visible red), an interferometric SAR (IfSAR) digital surface model, and lidar-derived canopy height to classify biomass density using both a three-class scheme (high, medium and low) and a two-class scheme (high and low). Elevation adjustments associated with these classes using both median and quartile approaches were applied to adjust lidar-derived elevation values closer tomore » true bare earth elevation. The performance of the method was tested on 229 elevation points in the lower Apalachicola River Marsh. The two-class quartile-based adjusted DEM produced the best results, reducing the RMS error in elevation from 0.65 m to 0.40 m, a 38% improvement. The raw mean errors for the lidar DEM and the adjusted DEM were 0.61 ± 0.24 m and 0.32 ± 0.24 m, respectively, thereby reducing the high bias by approximately 49%.« less

Estimation of peak discharge quantiles for selected annual exceedance probabilities in northeastern Illinois

USGS Publications Warehouse

Over, Thomas M.; Saito, Riki J.; Veilleux, Andrea G.; Sharpe, Jennifer B.; Soong, David T.; Ishii, Audrey L.

2016-06-28

This report provides two sets of equations for estimating peak discharge quantiles at annual exceedance probabilities (AEPs) of 0.50, 0.20, 0.10, 0.04, 0.02, 0.01, 0.005, and 0.002 (recurrence intervals of 2, 5, 10, 25, 50, 100, 200, and 500 years, respectively) for watersheds in Illinois based on annual maximum peak discharge data from 117 watersheds in and near northeastern Illinois. One set of equations was developed through a temporal analysis with a two-step least squares-quantile regression technique that measures the average effect of changes in the urbanization of the watersheds used in the study. The resulting equations can be used to adjust rural peak discharge quantiles for the effect of urbanization, and in this study the equations also were used to adjust the annual maximum peak discharges from the study watersheds to 2010 urbanization conditions.The other set of equations was developed by a spatial analysis. This analysis used generalized least-squares regression to fit the peak discharge quantiles computed from the urbanization-adjusted annual maximum peak discharges from the study watersheds to drainage-basin characteristics. The peak discharge quantiles were computed by using the Expected Moments Algorithm following the removal of potentially influential low floods defined by a multiple Grubbs-Beck test. To improve the quantile estimates, regional skew coefficients were obtained from a newly developed regional skew model in which the skew increases with the urbanized land use fraction. The drainage-basin characteristics used as explanatory variables in the spatial analysis include drainage area, the fraction of developed land, the fraction of land with poorly drained soils or likely water, and the basin slope estimated as the ratio of the basin relief to basin perimeter.This report also provides the following: (1) examples to illustrate the use of the spatial and urbanization-adjustment equations for estimating peak discharge quantiles at ungaged

Parenting and Late Adolescent Emotional Adjustment: Mediating Effects of Discipline and Gender

ERIC Educational Resources Information Center

McKinney, Cliff; Milone, Mary Catherine; Renk, Kimberly

2011-01-01

Research suggests that parenting styles are related to the types of discipline parents utilize and that the coupling of parenting styles and discipline techniques are related to child outcomes. Although extant research examines the effects of parenting styles and discipline on child and early adolescent adjustment, less is known about adjustment…

On the nullspace of TLS multi-station adjustment

NASA Astrophysics Data System (ADS)

Sterle, Oskar; Kogoj, Dušan; Stopar, Bojan; Kregar, Klemen

2018-07-01

In the article we present an analytic aspect of TLS multi-station least-squares adjustment with the main focus on the datum problem. The datum problem is, compared to previously published researches, theoretically analyzed and solved, where the solution is based on nullspace derivation of the mathematical model. The importance of datum problem solution is seen in a complete description of TLS multi-station adjustment solutions from a set of all minimally constrained least-squares solutions. On a basis of known nullspace, estimable parameters are described and the geometric interpretation of all minimally constrained least squares solutions is presented. At the end a simulated example is used to analyze the results of TLS multi-station minimally constrained and inner constrained least-squares adjustment solutions.

Effects of peer victimization on psychological and academic adjustment in early adolescence.

PubMed

Rueger, Sandra Yu; Jenkins, Lyndsay N

2014-03-01

The purpose of the current study is to investigate the effects of frequency of peer victimization experiences on psychological and academic adjustment during early adolescence, with a focus on testing psychological adjustment as a mediator, as well as differences based on gender and type of victimization. The sample in this short-term longitudinal design study consists of 7th and 8th graders (n = 670, 50% male) from an ethnically and socioeconomically diverse middle school. Victimization was measured using 10 items that assessed frequency of verbal, physical, and relational victimization experiences, and outcomes were assessed with the Behavior Assessment System for Children (2nd ed.) and school records. There was support for gender differences in frequency of peer victimization experiences based on type of victimization. More specifically, boys reported higher levels of physical and verbal victimization, and girls reported higher levels of relational victimization. In addition, there were statistically significant differences between boys and girls on the relation between victimization and anxiety, attendance, and grades, with girls experiencing more maladjustment than boys in response to peer victimization. Finally, results demonstrated no gender differences in indirect effects of psychological adjustment on the relation between peer victimization and academic outcomes, whether victimization was physical, verbal, and relational. These findings highlight the importance of addressing social-emotional functioning as well as peer victimization in the schools for both boys and girls, as both affect students' academic functioning. PsycINFO Database Record (c) 2014 APA, all rights reserved.

Essays in applied macroeconomics: Asymmetric price adjustment, exchange rate and treatment effect

NASA Astrophysics Data System (ADS)

Gu, Jingping

This dissertation consists of three essays. Chapter II examines the possible asymmetric response of gasoline prices to crude oil price changes using an error correction model with GARCH errors. Recent papers have looked at this issue. Some of these papers estimate a form of error correction model, but none of them accounts for autoregressive heteroskedasticity in estimation and testing for asymmetry and none of them takes the response of crude oil price into consideration. We find that time-varying volatility of gasoline price disturbances is an important feature of the data, and when we allow for asymmetric GARCH errors and investigate the system wide impulse response function, we find evidence of asymmetric adjustment to crude oil price changes in weekly retail gasoline prices. Chapter III discusses the relationship between fiscal deficit and exchange rate. Economic theory predicts that fiscal deficits can significantly affect real exchange rate movements, but existing empirical evidence reports only a weak impact of fiscal deficits on exchange rates. Based on US dollar-based real exchange rates in G5 countries and a flexible varying coefficient model, we show that the previously documented weak relationship between fiscal deficits and exchange rates may be the result of additive specifications, and that the relationship is stronger if we allow fiscal deficits to impact real exchange rates non-additively as well as nonlinearly. We find that the speed of exchange rate adjustment toward equilibrium depends on the state of the fiscal deficit; a fiscal contraction in the US can lead to less persistence in the deviation of exchange rates from fundamentals, and faster mean reversion to the equilibrium. Chapter IV proposes a kernel method to deal with the nonparametric regression model with only discrete covariates as regressors. This new approach is based on recently developed least squares cross-validation kernel smoothing method. It can not only automatically smooth

The Mediating Role of Psychological Adjustment between Peer Victimization and Social Adjustment in Adolescence

PubMed Central

Romera, Eva M.; Gómez-Ortiz, Olga; Ortega-Ruiz, Rosario

2016-01-01

There is extensive scientific evidence of the serious psychological and social effects that peer victimization may have on students, among them internalizing problems such as anxiety or negative self-esteem, difficulties related to low self-efficacy and lower levels of social adjustment. Although a direct relationship has been observed between victimization and these effects, it has not yet been analyzed whether there is a relationship of interdependence between all these measures of psychosocial adjustment. The aim of this study was to examine the relationship between victimization and difficulties related to social adjustment among high school students. To do so, various explanatory models were tested to determine whether psychological adjustment (negative self-esteem, social anxiety and social self-efficacy) could play a mediating role in this relationship, as suggested by other studies on academic adjustment. The sample comprised 2060 Spanish high school students (47.9% girls; mean age = 14.34). The instruments used were the scale of victimization from European Bullying Intervention Project Questionnaire, the negative scale from Rosenberg Self-Esteem Scale, Social Anxiety Scale for Adolescents and a general item about social self-efficacy, all of them self-reports. Structural equation modeling was used to analyze the data. The results confirmed the partial mediating role of negative self-esteem, social anxiety and social self-efficacy between peer victimization and social adjustment and highlight the importance of empowering victimized students to improve their self-esteem and self-efficacy and prevent social anxiety. Such problems lead to the avoidance of social interactions and social reinforcement, thus making it difficult for these students to achieve adequate social adjustment. PMID:27891108

The Mediating Role of Psychological Adjustment between Peer Victimization and Social Adjustment in Adolescence.

PubMed

Romera, Eva M; Gómez-Ortiz, Olga; Ortega-Ruiz, Rosario

2016-01-01

There is extensive scientific evidence of the serious psychological and social effects that peer victimization may have on students, among them internalizing problems such as anxiety or negative self-esteem, difficulties related to low self-efficacy and lower levels of social adjustment. Although a direct relationship has been observed between victimization and these effects, it has not yet been analyzed whether there is a relationship of interdependence between all these measures of psychosocial adjustment. The aim of this study was to examine the relationship between victimization and difficulties related to social adjustment among high school students. To do so, various explanatory models were tested to determine whether psychological adjustment (negative self-esteem, social anxiety and social self-efficacy) could play a mediating role in this relationship, as suggested by other studies on academic adjustment. The sample comprised 2060 Spanish high school students (47.9% girls; mean age = 14.34). The instruments used were the scale of victimization from European Bullying Intervention Project Questionnaire , the negative scale from Rosenberg Self-Esteem Scale, Social Anxiety Scale for Adolescents and a general item about social self-efficacy, all of them self-reports. Structural equation modeling was used to analyze the data. The results confirmed the partial mediating role of negative self-esteem, social anxiety and social self-efficacy between peer victimization and social adjustment and highlight the importance of empowering victimized students to improve their self-esteem and self-efficacy and prevent social anxiety. Such problems lead to the avoidance of social interactions and social reinforcement, thus making it difficult for these students to achieve adequate social adjustment.

Diagnosis-Based Risk Adjustment for Medicare Capitation Payments

PubMed Central

Ellis, Randall P.; Pope, Gregory C.; Iezzoni, Lisa I.; Ayanian, John Z.; Bates, David W.; Burstin, Helen; Ash, Arlene S.

1996-01-01

Using 1991-92 data for a 5-percent Medicare sample, we develop, estimate, and evaluate risk-adjustment models that utilize diagnostic information from both inpatient and ambulatory claims to adjust payments for aged and disabled Medicare enrollees. Hierarchical coexisting conditions (HCC) models achieve greater explanatory power than diagnostic cost group (DCG) models by taking account of multiple coexisting medical conditions. Prospective models predict average costs of individuals with chronic conditions nearly as well as concurrent models. All models predict medical costs far more accurately than the current health maintenance organization (HMO) payment formula. PMID:10172666

Is weight-based adjustment of automatic exposure control necessary for the reduction of chest CT radiation dose?

PubMed

Prakash, Priyanka; Kalra, Mannudeep K; Gilman, Matthew D; Shepard, Jo-Anne O; Digumarthy, Subba R

2010-01-01

To assess the effects of radiation dose reduction in the chest CT using a weight-based adjustment of the automatic exposure control (AEC) technique. With Institutional Review Board Approval, 60 patients (mean age, 59.1 years; M:F = 35:25) and 57 weight-matched patients (mean age, 52.3 years, M:F = 25:32) were scanned using a weight-adjusted AEC and non-weight-adjusted AEC, respectively on a 64-slice multidetector CT with a 0.984:1 pitch, 0.5 second rotation time, 40 mm table feed/rotation, and 2.5 mm section thickness. Patients were categorized into 3 weight categories; < 60 kg (n = 17), 60-90 kg (n = 52), and > 90 kg (n = 48). Patient weights, scanning parameters, CT dose index volumes (CTDIvol) and dose length product (DLP) were recorded, while effective dose (ED) was estimated. Image noise was measured in the descending thoracic aorta. Data were analyzed using a standard statistical package (SAS/STAT) (Version 9.1, SAS institute Inc, Cary, NC). Compared to the non-weight-adjusted AEC, the weight-adjusted AEC technique resulted in an average decrease of 29% in CTDIvol and a 27% effective dose reduction (p < 0.0001). With weight-adjusted AEC, the CTDIvol decreased to 15.8, 15.9, and 27.3 mGy for the < 60, 60-90 and > 91 kg weight groups, respectively, compared to 20.3, 27.9 and 32.8 mGy, with non-weight-adjusted AEC. No significant difference was observed for objective image noise between the chest CT acquired with the non-weight-adjusted (15.0 +/- 3.1) and weight-adjusted (16.1 +/- 5.6) AEC techniques (p > 0.05). The results of this study suggest that AEC should be tailored according to patient weight. Without weight-based adjustment of AEC, patients are exposed to a 17 - 43% higher radiation-dose from a chest CT.

ECCM Scheme against Interrupted Sampling Repeater Jammer Based on Parameter-Adjusted Waveform Design

PubMed Central

Wei, Zhenhua; Peng, Bo; Shen, Rui

2018-01-01

Interrupted sampling repeater jamming (ISRJ) is an effective way of deceiving coherent radar sensors, especially for linear frequency modulated (LFM) radar. In this paper, for a simplified scenario with a single jammer, we propose a dynamic electronic counter-counter measure (ECCM) scheme based on jammer parameter estimation and transmitted signal design. Firstly, the LFM waveform is transmitted to estimate the main jamming parameters by investigating the discontinuousness of the ISRJ’s time-frequency (TF) characteristics. Then, a parameter-adjusted intra-pulse frequency coded signal, whose ISRJ signal after matched filtering only forms a single false target, is designed adaptively according to the estimated parameters, i.e., sampling interval, sampling duration and repeater times. Ultimately, for typical jamming scenes with different jamming signal ratio (JSR) and duty cycle, we propose two particular ISRJ suppression approaches. Simulation results validate the effective performance of the proposed scheme for countering the ISRJ, and the trade-off relationship between the two approaches is demonstrated. PMID:29642508

Quantifying the impact of time-varying baseline risk adjustment in the self-controlled risk interval design.

PubMed

Li, Lingling; Kulldorff, Martin; Russek-Cohen, Estelle; Kawai, Alison Tse; Hua, Wei

2015-12-01

The self-controlled risk interval design is commonly used to assess the association between an acute exposure and an adverse event of interest, implicitly adjusting for fixed, non-time-varying covariates. Explicit adjustment needs to be made for time-varying covariates, for example, age in young children. It can be performed via either a fixed or random adjustment. The random-adjustment approach can provide valid point and interval estimates but requires access to individual-level data for an unexposed baseline sample. The fixed-adjustment approach does not have this requirement and will provide a valid point estimate but may underestimate the variance. We conducted a comprehensive simulation study to evaluate their performance. We designed the simulation study using empirical data from the Food and Drug Administration-sponsored Mini-Sentinel Post-licensure Rapid Immunization Safety Monitoring Rotavirus Vaccines and Intussusception study in children 5-36.9 weeks of age. The time-varying confounder is age. We considered a variety of design parameters including sample size, relative risk, time-varying baseline risks, and risk interval length. The random-adjustment approach has very good performance in almost all considered settings. The fixed-adjustment approach can be used as a good alternative when the number of events used to estimate the time-varying baseline risks is at least the number of events used to estimate the relative risk, which is almost always the case. We successfully identified settings in which the fixed-adjustment approach can be used as a good alternative and provided guidelines on the selection and implementation of appropriate analyses for the self-controlled risk interval design. Copyright © 2015 John Wiley & Sons, Ltd.

Assessing uncertainty in published risk estimates using ...

EPA Pesticide Factsheets

Introduction: The National Research Council recommended quantitative evaluation of uncertainty in effect estimates for risk assessment. This analysis considers uncertainty across model forms and model parameterizations with hexavalent chromium [Cr(VI)] and lung cancer mortality as an example. The objective is to characterize model uncertainty by evaluating estimates across published epidemiologic studies of the same cohort.Methods: This analysis was based on 5 studies analyzing a cohort of 2,357 workers employed from 1950-74 in a chromate production plant in Maryland. Cox and Poisson models were the only model forms considered by study authors to assess the effect of Cr(VI) on lung cancer mortality. All models adjusted for smoking and included a 5-year exposure lag, however other latency periods and model covariates such as age and race were considered. Published effect estimates were standardized to the same units and normalized by their variances to produce a standardized metric to compare variability within and between model forms. A total of 5 similarly parameterized analyses were considered across model form, and 16 analyses with alternative parameterizations were considered within model form (10 Cox; 6 Poisson). Results: Across Cox and Poisson model forms, adjusted cumulative exposure coefficients (betas) for 5 similar analyses ranged from 2.47 to 4.33 (mean=2.97, σ2=0.63). Within the 10 Cox models, coefficients ranged from 2.53 to 4.42 (mean=3.29, σ2=0.

Effects of Timing of Adversity on Adolescent and Young Adult Adjustment

ERIC Educational Resources Information Center

Kiff, Cara J.; Cortes, Rebecca C.; Lengua, Liliana J.; Kosterman, Rick; Hawkins, J. David; Mason, W. Alex

2012-01-01

Exposure to adversity during childhood and adolescence predicts adjustment across development. Furthermore, adolescent adjustment problems persist into young adulthood. This study examined relations of contextual adversity with concurrent adolescent adjustment and prospective mental health and health outcomes in young adulthood. A longitudinal…

The effect of low force chiropractic adjustments for 4 weeks on body surface electromagnetic field.

PubMed

Zhang, John; Snyder, Brian J

2005-01-01

To study the effects of 4 weeks of low-force chiropractic adjustments on body surface electromagnetic fields (EMFs). Thirty-five chiropractic students randomly assigned into control (17 subjects) and experimental groups (28 subjects). A triaxial fluxgate magnetometer was used for EMF detection. The subjects' body surface EMF was determined in the prone position before and after the chiropractic adjustment. A Toftness low-force chiropractic adjustment was applied to the cervical, thoracic, lumbar, and sacral areas as determined by the practitioner. Heart rate variability analysis was recorded once a week to determine autonomic nervous system activity in both the control and experimental groups. The EMF on the subjects' body surface decreased after chiropractic adjustment at the cervical, thoracic, lumbar, and sacral regions in all 6 visits during the 4-week treatment period. The EMF showed a downtrend over the 4-week period after the low-force adjustment. The same changes were not observed in the control group. The chiropractic adjustment group had a slight decrease in heart rate over the 4-week treatment period, and no significant change was observed in the control group. Heart rate variability analysis did not show consistent changes before and after the low-force adjustments during the treatment period. Low-force chiropractic adjustment in the cervical and thoracic areas resulted in a consistent reduction of the body surface EMF after 4 weeks of active treatment. No statistically significant differences were found in the heart rate and heart rate variability in the 4-week study.

Impact of Disease Prevalence Adjustment on Hospitalization Rates for Chronic Ambulatory Care-Sensitive Conditions in Germany.

PubMed

Pollmanns, Johannes; Romano, Patrick S; Weyermann, Maria; Geraedts, Max; Drösler, Saskia E

2018-04-01

To explore effects of disease prevalence adjustment on ambulatory care-sensitive hospitalization (ACSH) rates used for quality comparisons. County-level hospital administrative data on adults discharged from German hospitals in 2011 and prevalence estimates based on administrative ambulatory diagnosis data were used. A retrospective cross-sectional study using in- and outpatient secondary data was performed. Hospitalization data for hypertension, diabetes, heart failure, chronic obstructive pulmonary disease, and asthma were obtained from the German Diagnosis Related Groups (DRG) database. Prevalence estimates were obtained from the German Central Research Institute of Ambulatory Health Care. Crude hospitalization rates varied substantially across counties (coefficients of variation [CV] 28-37 percent across conditions); this variation was reduced by prevalence adjustment (CV 21-28 percent). Prevalence explained 40-50 percent of the observed variation (r = 0.65-0.70) in ACSH rates for all conditions except asthma (r = 0.07). Between 30 percent and 38 percent of areas moved into or outside condition-specific control limits with prevalence adjustment. Unadjusted ACSH rates should be used with caution for high-stakes public reporting as differences in prevalence may have a marked impact. Prevalence adjustment should be considered in models analyzing ACSH. © Health Research and Educational Trust.

Impact of statistical adjustment for frequency of venue attendance in a venue-based survey of men who have sex with men.

PubMed

Gustafson, Paul; Gilbert, Mark; Xia, Michelle; Michelow, Warren; Robert, Wayne; Trussler, Terry; McGuire, Marissa; Paquette, Dana; Moore, David M; Gustafson, Reka

2013-05-15

Venue sampling is a common sampling method for populations of men who have sex with men (MSM); however, men who visit venues frequently are more likely to be recruited. While statistical adjustment methods are recommended, these have received scant attention in the literature. We developed a novel approach to adjust for frequency of venue attendance (FVA) and assess the impact of associated bias in the ManCount Study, a venue-based survey of MSM conducted in Vancouver, British Columbia, Canada, in 2008-2009 to measure the prevalence of human immunodeficiency virus and other infections and associated behaviors. Sampling weights were determined from an abbreviated list of questions on venue attendance and were used to adjust estimates of prevalence for health and behavioral indicators using a Bayesian, model-based approach. We found little effect of FVA adjustment on biological or sexual behavior indicators (primary outcomes); however, adjustment for FVA did result in differences in the prevalence of demographic indicators, testing behaviors, and a small number of additional variables. While these findings are reassuring and lend credence to unadjusted prevalence estimates from this venue-based survey, adjustment for FVA did shed important insights on MSM subpopulations that were not well represented in the sample.

The Effects Behavior Problems in Preschool Children Have on Their School Adjustment

ERIC Educational Resources Information Center

Yoleri, Sibel

2013-01-01

This research is conducted to examine the predictor effects the behavior problem level has on the school adjustment variable. With this objective, the sample research group consists of 136 children (having normal growth) between 5-6 years old attending preschools affiliated with the Ministry of National Education, and located in the city centre of…

Spousal Adjustment to Myocardial Infarction.

ERIC Educational Resources Information Center

Ziglar, Elisa J.

This paper reviews the literature on the stresses and coping strategies of spouses of patients with myocardial infarction (MI). It attempts to identify specific problem areas of adjustment for the spouse and to explore the effects of spousal adjustment on patient recovery. Chapter one provides an overview of the importance in examining the…

Positive Adjustment Among American Repatriated Prisoners of the Vietnam War: Modeling the Long-Term Effects of Captivity.

PubMed

King, Daniel W; King, Lynda A; Park, Crystal L; Lee, Lewina O; Kaiser, Anica Pless; Spiro, Avron; Moore, Jeffrey L; Kaloupek, Danny G; Keane, Terence M

2015-11-01

A longitudinal lifespan model of factors contributing to later-life positive adjustment was tested on 567 American repatriated prisoners from the Vietnam War. This model encompassed demographics at time of capture and attributes assessed after return to the U.S. (reports of torture and mental distress) and approximately 3 decades later (later-life stressors, perceived social support, positive appraisal of military experiences, and positive adjustment). Age and education at time of capture and physical torture were associated with repatriation mental distress, which directly predicted poorer adjustment 30 years later. Physical torture also had a salutary effect, enhancing later-life positive appraisals of military experiences. Later-life events were directly and indirectly (through concerns about retirement) associated with positive adjustment. Results suggest that the personal resources of older age and more education and early-life adverse experiences can have cascading effects over the lifespan to impact well-being in both positive and negative ways.

Positive Adjustment Among American Repatriated Prisoners of the Vietnam War: Modeling the Long-Term Effects of Captivity

PubMed Central

King, Daniel W.; King, Lynda A.; Park, Crystal L.; Lee, Lewina O.; Kaiser, Anica Pless; Spiro, Avron; Moore, Jeffrey L.; Kaloupek, Danny G.; Keane, Terence M.

2015-01-01

A longitudinal lifespan model of factors contributing to later-life positive adjustment was tested on 567 American repatriated prisoners from the Vietnam War. This model encompassed demographics at time of capture and attributes assessed after return to the U.S. (reports of torture and mental distress) and approximately 3 decades later (later-life stressors, perceived social support, positive appraisal of military experiences, and positive adjustment). Age and education at time of capture and physical torture were associated with repatriation mental distress, which directly predicted poorer adjustment 30 years later. Physical torture also had a salutary effect, enhancing later-life positive appraisals of military experiences. Later-life events were directly and indirectly (through concerns about retirement) associated with positive adjustment. Results suggest that the personal resources of older age and more education and early-life adverse experiences can have cascading effects over the lifespan to impact well-being in both positive and negative ways. PMID:26693100

Health-adjusted life expectancy in Canada.

PubMed

Bushnik, Tracey; Tjepkema, Michael; Martel, Laurent

2018-04-18

Over the past century, life expectancy at birth in Canada has risen substantially. However, these gains in the quantity of life say little about gains in the quality of life. Health-adjusted life expectancy (HALE), an indicator of quality of life, was estimated for the household and institutional populations combined every four years from 1994/1995 to 2015. Health status was measured by the Health Utilities Index Mark 3 instrument in two national population health surveys, and was used to adjust life expectancy. The percentage of the population living in health-related institutions was estimated based on the Census of Population. Attribute-deleted HALE was calculated to determine how various aspects of health status contributed to the differences between life expectancy and HALE. HALE has increased in Canada. Greater gains among males have narrowed the gap between males and females. The ratio of HALE to life expectancy changed little for males, and a marginal improvement was observed for females aged 65 or older. Mobility problems and pain, the latter mainly among females, accounted for an increased share of the burden of ill health over time. Exclusion of the institutional population significantly increased the estimates of HALE and yielded higher ratios of HALE to life expectancy. Although people are living longer, the share of years spent in good functional health has remained fairly constant. Data for both the household and institutional populations are necessary for a complete picture of health expectancy in Canada.

Regression equations for estimation of annual peak-streamflow frequency for undeveloped watersheds in Texas using an L-moment-based, PRESS-minimized, residual-adjusted approach

USGS Publications Warehouse

Asquith, William H.; Roussel, Meghan C.

2009-01-01

Annual peak-streamflow frequency estimates are needed for flood-plain management; for objective assessment of flood risk; for cost-effective design of dams, levees, and other flood-control structures; and for design of roads, bridges, and culverts. Annual peak-streamflow frequency represents the peak streamflow for nine recurrence intervals of 2, 5, 10, 25, 50, 100, 200, 250, and 500 years. Common methods for estimation of peak-streamflow frequency for ungaged or unmonitored watersheds are regression equations for each recurrence interval developed for one or more regions; such regional equations are the subject of this report. The method is based on analysis of annual peak-streamflow data from U.S. Geological Survey streamflow-gaging stations (stations). Beginning in 2007, the U.S. Geological Survey, in cooperation with the Texas Department of Transportation and in partnership with Texas Tech University, began a 3-year investigation concerning the development of regional equations to estimate annual peak-streamflow frequency for undeveloped watersheds in Texas. The investigation focuses primarily on 638 stations with 8 or more years of data from undeveloped watersheds and other criteria. The general approach is explicitly limited to the use of L-moment statistics, which are used in conjunction with a technique of multi-linear regression referred to as PRESS minimization. The approach used to develop the regional equations, which was refined during the investigation, is referred to as the 'L-moment-based, PRESS-minimized, residual-adjusted approach'. For the approach, seven unique distributions are fit to the sample L-moments of the data for each of 638 stations and trimmed means of the seven results of the distributions for each recurrence interval are used to define the station specific, peak-streamflow frequency. As a first iteration of regression, nine weighted-least-squares, PRESS-minimized, multi-linear regression equations are computed using the watershed

Developing Analogy Cost Estimates for Space Missions

NASA Technical Reports Server (NTRS)

Shishko, Robert

2004-01-01

The analogy approach in cost estimation combines actual cost data from similar existing systems, activities, or items with adjustments for a new project's technical, physical or programmatic differences to derive a cost estimate for the new system. This method is normally used early in a project cycle when there is insufficient design/cost data to use as a basis for (or insufficient time to perform) a detailed engineering cost estimate. The major limitation of this method is that it relies on the judgment and experience of the analyst/estimator. The analyst must ensure that the best analogy or analogies have been selected, and that appropriate adjustments have been made. While analogy costing is common, there is a dearth of advice in the literature on the 'adjustment methodology', especially for hardware projects. This paper discusses some potential approaches that can improve rigor and repeatability in the analogy costing process.

Adjusting forest density estimates for surveyor bias in historical tree surveys

Treesearch

Brice B. Hanberry; Jian Yang; John M. Kabrick; Hong S. He

2012-01-01

The U.S. General Land Office surveys, conducted between the late 1700s to early 1900s, provide records of trees prior to widespread European and American colonial settlement. However, potential and documented surveyor bias raises questions about the reliability of historical tree density estimates and other metrics based on density estimated from these records. In this...

Pseudoephedrine: effects on milk production in women and estimation of infant exposure via breastmilk

PubMed Central

Aljazaf, Khalidah; Hale, Thomas W; Ilett, Kenneth F; Hartmann, Peter E; Mitoulas, Leon R; Kristensen, Judith H; Hackett, L Peter

2003-01-01

Aims To assess the effects of pseudoephedrine on breast blood flow, temperature and milk production, and to estimate the likely infant dose during breastfeeding. Methods Eight lactating women (mean age 35 years and weight 69 kg) participated in a single-blind randomized crossover study of 60 mg pseudoephedrine hydrochloride vs placebo. Breast blood flow and surface temperature were measured from 0 to 4 h following the dose, and change in plasma prolactin was measured as the difference between predose and 1 h postdose concentrations. Milk production was measured for 24 h following placebo and pseudoephedrine. Infant dose of pseudoephedrine for a 60-mg dose administered four times daily to the mother was quantified as the product of average steady-state drug concentration in milk and an estimated milk production rate of 0.15 l kg−1 day−1 and expressed relative to the maternal weight-adjusted dose. Results There were no physiologically significant changes in breast blood flow or temperature between the placebo and pseudoephedrine periods. The mean change in plasma prolactin was slightly (13.5%), but not significantly lower (t = 1.245, P = 0.253) after pseudoephedrine (1775 mU l−1) compared with placebo (2014 mU l−1). However, the mean milk volume was reduced by 24% from 784 ml day−1 in the placebo period to 623 ml day−1 in the pseudoephedrine period (difference between means 161 ml day−1 (95% CI: 63, 259 ml day−1); t = 3.9, P = 0.006). Assuming maternal intake of 60 mg pseudoephedrine hydrochloride four times daily, the estimated infant dose of pseudoephedrine was 4.3% (95% CI, 3.2, 5.4%) of the weight-adjusted maternal dose. Conclusions A single dose of pseudoephedrine significantly reduced milk production. This effect was not attributable to changes in blood flow, but depression of prolactin secretion may be a contributing factor. At the maximum recommended pseudoephedrine doses, the calculated infant dose delivered via milk was < 10% of the maternal

A simple signaling rule for variable life-adjusted display derived from an equivalent risk-adjusted CUSUM chart.

PubMed

Wittenberg, Philipp; Gan, Fah Fatt; Knoth, Sven

2018-04-17

The variable life-adjusted display (VLAD) is the first risk-adjusted graphical procedure proposed in the literature for monitoring the performance of a surgeon. It displays the cumulative sum of expected minus observed deaths. It has since become highly popular because the statistic plotted is easy to understand. But it is also easy to misinterpret a surgeon's performance by utilizing the VLAD, potentially leading to grave consequences. The problem of misinterpretation is essentially caused by the variance of the VLAD's statistic that increases with sample size. In order for the VLAD to be truly useful, a simple signaling rule is desperately needed. Various forms of signaling rules have been developed, but they are usually quite complicated. Without signaling rules, making inferences using the VLAD alone is difficult if not misleading. In this paper, we establish an equivalence between a VLAD with V-mask and a risk-adjusted cumulative sum (RA-CUSUM) chart based on the difference between the estimated probability of death and surgical outcome. Average run length analysis based on simulation shows that this particular RA-CUSUM chart has similar performance as compared to the established RA-CUSUM chart based on the log-likelihood ratio statistic obtained by testing the odds ratio of death. We provide a simple design procedure for determining the V-mask parameters based on a resampling approach. Resampling from a real data set ensures that these parameters can be estimated appropriately. Finally, we illustrate the monitoring of a real surgeon's performance using VLAD with V-mask. Copyright © 2018 John Wiley & Sons, Ltd.

The effect of acquiring life skills through humor on social adjustment rate of the female students.

PubMed

Maghsoudi, Jahangir; Sabour, Nazanin Hashemi; Yazdani, Mohsen; Mehrabi, Tayebeh

2010-01-01

Life skills have different effects on various aspects of the mental health. Social adjustment prepares adolescents for entering to the adulthood. On the other hand, humor and joking in the education is considered as a stress reducer and learning increaser. Therefore, the present study conducted aimed to determine the effect of acquiring life skills through humor on the social adjustment rate of the high school girls. This was a two-group semi-experimental study including three phases. The study population included 69 first year high school female students of Isfahan Department of Education district 3 who were selected in simple random sampling. First of all, the social adjustment rate was measured using California Personality Inventory. Thereafter, life skills education was conducted using humor during five sessions. Finally, a test was taken in order to assess the acquisition of the life skills in which passing score was required for re-completing the questionnaire. The data were analyzed using software SPSS(10) and independent and paired t-tests. The findings of the study indicated that the mean score of the social adjustment statistically had a significant difference in the intervention group before and after the intervention. Furthermore, statistically, there was a significant difference between mean score of the social adjustment in the control group and test group after conducting the intervention. The findings of the study indicated that life skills education has been increased through humor on the social adjustment rate of the high school girl students. Considering the efficacy of learning life skills on the social adjustment and results of the other studies which were in accordance with the present study, implementing such trainings with a new method comprehensively is recommended in the schools.

Effect of Fixed Versus Adjusted Transcutaneous Electrical Nerve Stimulation Amplitude on Chronic Mechanical Low Back Pain.

PubMed

Elserty, Noha; Kattabei, Omaima; Elhafez, Hytham

2016-07-01

This study aimed to investigate the effect of adjusting pulse amplitude of transcutaneous electrical nerve stimulation versus fixed pulse amplitude in treatment of chronic mechanical low back pain. Randomized clinical trial. El-sahel Teaching Hospital, Egypt. Forty-five patients with chronic low back pain assigned to three equal groups. Their ages ranged from 20 to 50 years. The three groups received the same exercise program. Group A received transcutaneous electrical nerve stimulation with fixed pulse amplitude for 40 minutes. Group B received transcutaneous electrical nerve stimulation with adjusted pulse amplitude for 40 minutes, with the pulse amplitude adjusted every 5 minutes. Group C received exercises only. Treatment sessions were applied three times per week for 4 weeks for the three groups. A visual analogue scale was used to assess pain severity, the Oswestry Disability Index was used to assess functional level, and a dual inclinometer was used to measure lumbar range of motion. Evaluations were performed before and after treatment. Visual analogue scale, Oswestry Disability Index, and back range of motion significantly differed between the two groups that received transcutaneous electrical nerve stimulation and the control group and did not significantly differ between fixed and adjusted pulse amplitude of transcutaneous electrical nerve stimulation. Adjusting pulse amplitude of transcutaneous electrical nerve stimulation does not produce a difference in the effect of transcutaneous electrical nerve stimulation used to treat chronic low back pain.

Estimates of 2012/13 influenza vaccine effectiveness using the case test-negative control design with different influenza negative control groups.

PubMed

Nunes, Baltazar; Machado, Ausenda; Guiomar, Raquel; Pechirra, Pedro; Conde, Patrícia; Cristovão, Paula; Falcão, Isabel

2014-07-31

In recent years several reports of influenza vaccine effectiveness (VE) have been made early for public health decision. The majority of these studies use the case test-negative control design (TND), which has been showed to provide, under certain conditions, unbiased estimates of influenza VE. Nevertheless, discussions have been taken on the best influenza negative control group to use. The present study aims to contribute to the knowledge on this field by comparing influenza VE estimates using three test-negative controls: all influenza negative, non-influenza respiratory virus and pan-negative. Incident ILI patients were prospectively selected and swabbed by a sample of general practitioners. Cases were ILI patients tested positive for influenza and controls ILI patients tested negative for influenza. The influenza negative control group was divided into non-influenza virus control group and pan-negative control group. Data were collected on vaccination status and confounding factors. Influenza VE was estimated as one minus the odds ratio of been vaccinated in cases versus controls adjusted for confounding effect by logistic regression. Confounder adjusted influenza VE against medically attended laboratory-confirmed influenza was 68.4% (95% CI: 20.7-87.4%) using all influenza negatives controls, 82.1% (95% CI: 47.6-93.9%) using non-influenza controls and 49.4% (95% CI: -44.7% to 82.3%) using pan-negative controls. Influenza VE estimates differed according to the influenza negative control group used. These results are in accordance with the expected under the hypothesis of differential viral interference between influenza vaccinated and unvaccinated individuals. Given the wide importance of TND study further studies should be conducted in order to clarify the observed differences. Copyright © 2014 Elsevier Ltd. All rights reserved.

Costs of cervical cancer treatment: population-based estimates from Ontario

PubMed Central

Pendrith, C.; Thind, A.; Zaric, G.S.; Sarma, S.

2016-01-01

Objectives The objectives of the present study were to estimate the overall and specific medical care costs associated with cervical cancer in the first 5 years after diagnosis in Ontario. Methods Incident cases of invasive cervical cancer during 2007–2010 were identified from the Ontario Cancer Registry and linked to administrative databases held at the Institute for Clinical Evaluative Sciences. Mean costs in 2010 Canadian dollars were estimated using the arithmetic mean and estimators that adjust for censored data. Results Mean age of the patients in the study cohort (779 cases) was 49.3 years. The mean overall medical care cost was $39,187 [standard error (se): $1,327] in the 1st year after diagnosis. Costs in year 1 ranged from $34,648 (se: $1,275) for those who survived at least 1 year to $69,142 (se: $4,818) for those who died from cervical cancer within 1 year. At 5 years after diagnosis, the mean overall unadjusted cost was $63,131 (se: $3,131), and the cost adjusted for censoring was $68,745 (se: $2,963). Inpatient hospitalizations and cancer-related care were the two largest components of cancer treatment costs. Conclusions We found that the estimated mean costs that did not account for censoring were consistently undervalued, highlighting the importance of estimates based on censoring-adjusted costs in cervical cancer. Our results are reliable for estimating the economic burden of cervical cancer and the cost-effectiveness of cervical cancer prevention strategies. PMID:27122978

Clinical antibacterial effectiveness of the self-adjusting file system.

PubMed

Neves, M A S; Rôças, I N; Siqueira, J F

2014-04-01

To evaluate in vivo the antibacterial effectiveness of the self-adjusting file (SAF) using molecular methods. Root canals from single-rooted teeth with apical periodontitis were instrumented using the SAF system under continuous irrigation with 2.5% NaOCl. DNA extracts from samples taken before and after instrumentation were subjected to quantitative analysis of total bacteria counts and levels of streptococci by quantitative real-time polymerase chain reaction (qPCR). The reverse-capture checkerboard assay was also used to identify 28 bacterial taxa before (S1) and after (S2) SAF instrumentation. SAF was also compared with a conventional hand nickel-titanium instrumentation technique for total bacterial reduction. Data from qPCR were analysed statistically within groups using the Wilcoxon matched pairs test and between groups using the Mann-Whitney U-test and the Fisher's exact test, with significance level set at P < 0.05. Self-adjusting file significantly reduced the total bacterial counts from a mean number of 1.96 × 10(7) cells to 1.34 × 10(4) cells (P < 0.001). Quantitatively, the 99.9% reduction in total bacterial counts associated with the SAF system was significantly superior to the 95.1% reduction obtained by hand instrumentation (P < 0.001). Qualitatively, SAF resulted in significantly more cases with negative PCR results for bacteria (54.5%) than hand instrumentation (4.5%) (P < 0.001). The SAF system succeeded in significantly reducing the streptococcal levels, but four cases still harboured these bacteria in S2. Checkerboard analysis revealed that not only streptococci but also some anaerobic and even as-yet-uncultivated bacteria may resist the effects of chemomechanical procedures. The SAF instrumentation system was highly effective in reducing bacterial populations from infected root canals and performed significantly better than hand instrumentation. However, because half of the samples still had detectable bacteria after preparation with SAF

Burden of Six Healthcare-Associated Infections on European Population Health: Estimating Incidence-Based Disability-Adjusted Life Years through a Population Prevalence-Based Modelling Study

PubMed Central

Eckmanns, Tim; Abu Sin, Muna; Ducomble, Tanja; Harder, Thomas; Sixtensson, Madlen; Velasco, Edward; Weiß, Bettina; Kramarz, Piotr; Monnet, Dominique L.; Kretzschmar, Mirjam E.; Suetens, Carl

2016-01-01

Background Estimating the burden of healthcare-associated infections (HAIs) compared to other communicable diseases is an ongoing challenge given the need for good quality data on the incidence of these infections and the involved comorbidities. Based on the methodology of the Burden of Communicable Diseases in Europe (BCoDE) project and 2011–2012 data from the European Centre for Disease Prevention and Control (ECDC) point prevalence survey (PPS) of HAIs and antimicrobial use in European acute care hospitals, we estimated the burden of six common HAIs. Methods and Findings The included HAIs were healthcare-associated pneumonia (HAP), healthcare-associated urinary tract infection (HA UTI), surgical site infection (SSI), healthcare-associated Clostridium difficile infection (HA CDI), healthcare-associated neonatal sepsis, and healthcare-associated primary bloodstream infection (HA primary BSI). The burden of these HAIs was measured in disability-adjusted life years (DALYs). Evidence relating to the disease progression pathway of each type of HAI was collected through systematic literature reviews, in order to estimate the risks attributable to HAIs. For each of the six HAIs, gender and age group prevalence from the ECDC PPS was converted into incidence rates by applying the Rhame and Sudderth formula. We adjusted for reduced life expectancy within the hospital population using three severity groups based on McCabe score data from the ECDC PPS. We estimated that 2,609,911 new cases of HAI occur every year in the European Union and European Economic Area (EU/EEA). The cumulative burden of the six HAIs was estimated at 501 DALYs per 100,000 general population each year in EU/EEA. HAP and HA primary BSI were associated with the highest burden and represented more than 60% of the total burden, with 169 and 145 DALYs per 100,000 total population, respectively. HA UTI, SSI, HA CDI, and HA primary BSI ranked as the third to sixth syndromes in terms of burden of disease

Covariate-adjusted Spearman's rank correlation with probability-scale residuals.

PubMed

Liu, Qi; Li, Chun; Wanga, Valentine; Shepherd, Bryan E

2018-06-01

It is desirable to adjust Spearman's rank correlation for covariates, yet existing approaches have limitations. For example, the traditionally defined partial Spearman's correlation does not have a sensible population parameter, and the conditional Spearman's correlation defined with copulas cannot be easily generalized to discrete variables. We define population parameters for both partial and conditional Spearman's correlation through concordance-discordance probabilities. The definitions are natural extensions of Spearman's rank correlation in the presence of covariates and are general for any orderable random variables. We show that they can be neatly expressed using probability-scale residuals (PSRs). This connection allows us to derive simple estimators. Our partial estimator for Spearman's correlation between X and Y adjusted for Z is the correlation of PSRs from models of X on Z and of Y on Z, which is analogous to the partial Pearson's correlation derived as the correlation of observed-minus-expected residuals. Our conditional estimator is the conditional correlation of PSRs. We describe estimation and inference, and highlight the use of semiparametric cumulative probability models, which allow preservation of the rank-based nature of Spearman's correlation. We conduct simulations to evaluate the performance of our estimators and compare them with other popular measures of association, demonstrating their robustness and efficiency. We illustrate our method in two applications, a biomarker study and a large survey. © 2017, The International Biometric Society.

Effects of inflammatory bowel disease on students' adjustment to college.

PubMed

Almadani, S Bashar; Adler, Jeremy; Browning, Jeff; Green, Elan H; Helvie, Karla; Rizk, Rafat S; Zimmermann, Ellen M

2014-12-01

Successful adjustment to college is required for academic success. We investigated whether inflammatory bowel disease (IBD) activity affects this adjustment process. We created an online survey that included a Student Adaptation to College Questionnaire (SACQ), a general quality of life survey (SF-12), a disease-specific short IBD quality of life survey (SIBDQ), and disease activity indices. Undergraduate students across the United States were recruited via social media. Surveys were completed by 65 students with Crohn's disease (CD), 28 with ulcerative colitis, and 214 healthy students (controls). Disease-specific quality of life (SIBDQ results) correlated with IBD disease activity (rho = -0.79; P < .0001). High college adjustment scores (SACQ results) were associated with high SIBDQ scores. Students with IBD had lower mean SACQ scores than controls (307 vs 290; P < .0001). There was a modest inverse correlation between CD activity and SACQ (rho = -0.24; P < .04). Disease activity in students with CD was associated strongly with their self-reported ability to keep up with academic work (P < .0089) and confidence in their ability to meet future academic challenges (P < .0015). Students with active IBD reported feeling as if they were not academically successful (P < .018), and students with ulcerative colitis reported irregular class attendance (P < .043). Students with IBD do not adjust to college as well as healthy students. Disease activity affects their adjustment and attitudes about academics-especially among students with CD. Successful adjustment is important for academic success, affecting graduation rates and future economic success. Strategies to increase disease control and provide social and emotional support during college could improve adjustment to college and academic performance, and increase patients' potential. Copyright © 2014 AGA Institute. Published by Elsevier Inc. All rights reserved.

Simulation-Based Estimates of the Effectiveness and Cost-Effectiveness of Pulmonary Rehabilitation in Patients with Chronic Obstructive Pulmonary Disease in France.

PubMed

Atsou, Kokuvi; Crequit, Perrine; Chouaid, Christos; Hejblum, Gilles

2016-01-01

The medico-economic impact of pulmonary rehabilitation in patients with chronic obstructive pulmonary disease (COPD) is poorly documented. To estimate the effectiveness and cost-effectiveness of pulmonary rehabilitation in a hypothetical cohort of COPD patients. We used a multi-state Markov model, adopting society's perspective. Simulated cohorts of French GOLD stage 2 to 4 COPD patients with and without pulmonary rehabilitation were compared in terms of life expectancy, quality-adjusted life years (QALY), disease-related costs, and the incremental cost-effectiveness ratio (ICER). Sensitivity analyses included variations of key model parameters. At the horizon of a COPD patient's remaining lifetime, pulmonary rehabilitation would result in mean gain of 0.8 QALY, with an over disease-related costs of 14 102 € per patient. The ICER was 17 583 €/QALY. Sensitivity analysis showed that pulmonary rehabilitation was cost-effective in every scenario (ICER <50 000 €/QALY). These results should provide a useful basis for COPD pulmonary rehabilitation programs.

Control adjustments in speaking: Electrophysiology of the Gratton effect in picture naming.

PubMed

Shitova, Natalia; Roelofs, Ardi; Schriefers, Herbert; Bastiaansen, Marcel; Schoffelen, Jan-Mathijs

2017-07-01

Accumulating evidence suggests that spoken word production requires different amounts of top-down control depending on the prevailing circumstances. For example, during Stroop-like tasks, the interference in response time (RT) is typically larger following congruent trials than following incongruent trials. This effect is called the Gratton effect, and has been taken to reflect top-down control adjustments based on the previous trial type. Such control adjustments have been studied extensively in Stroop and Eriksen flanker tasks (mostly using manual responses), but not in the picture-word interference (PWI) task, which is a workhorse of language production research. In one of the few studies of the Gratton effect in PWI, Van Maanen and Van Rijn (2010) examined the effect in picture naming RTs during dual-task performance. Based on PWI effect differences between dual-task conditions, they argued that the functional locus of the PWI effect differs between post-congruent trials (i.e., locus in perceptual and conceptual encoding) and post-incongruent trials (i.e., locus in word planning). However, the dual-task procedure may have contaminated the results. We therefore performed an electroencephalography (EEG) study on the Gratton effect in a regular PWI task. We observed a PWI effect in the RTs, in the N400 component of the event-related brain potentials, and in the midfrontal theta power, regardless of the previous trial type. Moreover, the RTs, N400, and theta power reflected the Gratton effect. These results provide evidence that the PWI effect arises at the word planning stage following both congruent and incongruent trials, while the amount of top-down control changes depending on the previous trial type. Copyright © 2017 Elsevier Ltd. All rights reserved.

Long-Term Quantitative Precipitation Estimates (QPE) at High Spatial and Temporal Resolution over CONUS: Bias-Adjustment of the Radar-Only National Mosaic and Multi-sensor QPE (NMQ/Q2) Precipitation Reanalysis (2001-2012)

NASA Astrophysics Data System (ADS)

Prat, Olivier; Nelson, Brian; Stevens, Scott; Seo, Dong-Jun; Kim, Beomgeun

2015-04-01

The processing of radar-only precipitation via the reanalysis from the National Mosaic and Multi-Sensor Quantitative (NMQ/Q2) based on the WSR-88D Next-generation Radar (NEXRAD) network over Continental United States (CONUS) is completed for the period covering from 2001 to 2012. This important milestone constitutes a unique opportunity to study precipitation processes at a 1-km spatial resolution for a 5-min temporal resolution. However, in order to be suitable for hydrological, meteorological and climatological applications, the radar-only product needs to be bias-adjusted and merged with in-situ rain gauge information. Several in-situ datasets are available to assess the biases of the radar-only product and to adjust for those biases to provide a multi-sensor QPE. The rain gauge networks that are used such as the Global Historical Climatology Network-Daily (GHCN-D), the Hydrometeorological Automated Data System (HADS), the Automated Surface Observing Systems (ASOS), and the Climate Reference Network (CRN), have different spatial density and temporal resolution. The challenges related to incorporating non-homogeneous networks over a vast area and for a long-term record are enormous. Among the challenges we are facing are the difficulties incorporating differing resolution and quality surface measurements to adjust gridded estimates of precipitation. Another challenge is the type of adjustment technique. The objective of this work is threefold. First, we investigate how the different in-situ networks can impact the precipitation estimates as a function of the spatial density, sensor type, and temporal resolution. Second, we assess conditional and un-conditional biases of the radar-only QPE for various time scales (daily, hourly, 5-min) using in-situ precipitation observations. Finally, after assessing the bias and applying reduction or elimination techniques, we are using a unique in-situ dataset merging the different RG networks (CRN, ASOS, HADS, GHCN-D) to

Combining QMRA and Epidemiology to Estimate Campylobacteriosis Incidence.

PubMed

Evers, Eric G; Bouwknegt, Martijn

2016-10-01

The disease burden of pathogens as estimated by QMRA (quantitative microbial risk assessment) and EA (epidemiological analysis) often differs considerably. This is an unsatisfactory situation for policymakers and scientists. We explored methods to obtain a unified estimate using campylobacteriosis in the Netherlands as an example, where previous work resulted in estimates of 4.9 million (QMRA) and 90,600 (EA) cases per year. Using the maximum likelihood approach and considering EA the gold standard, the QMRA model could produce the original EA estimate by adjusting mainly the dose-infection relationship. Considering QMRA the gold standard, the EA model could produce the original QMRA estimate by adjusting mainly the probability that a gastroenteritis case is caused by Campylobacter. A joint analysis of QMRA and EA data and models assuming identical outcomes, using a frequentist or Bayesian approach (using vague priors), resulted in estimates of 102,000 or 123,000 campylobacteriosis cases per year, respectively. These were close to the original EA estimate, and this will be related to the dissimilarity in data availability. The Bayesian approach further showed that attenuating the condition of equal outcomes immediately resulted in very different estimates of the number of campylobacteriosis cases per year and that using more informative priors had little effect on the results. In conclusion, EA was dominant in estimating the burden of campylobacteriosis in the Netherlands. However, it must be noted that only statistical uncertainties were taken into account here. Taking all, usually difficult to quantify, uncertainties into account might lead to a different conclusion. © 2016 Society for Risk Analysis.

Adjustment to College in Students with ADHD

ERIC Educational Resources Information Center

Rabiner, David L.; Anastopoulos, Arthur D.; Costello, Jane; Hoyle, Rick H.; Swartzwelder, H. Scott

2008-01-01

Objective: To examine college adjustment in students reporting an ADHD diagnosis and the effect of medication treatment on students' adjustment. Method: 1,648 first-semester freshmen attending a public and a private university completed a Web-based survey to examine their adjustment to college. Results: Compared with 200 randomly selected control…

Veterans Affairs facility performance on Washington Circle indicators and casemix-adjusted effectiveness.

PubMed

Harris, Alex H S; Humphreys, Keith; Finney, John W

2007-12-01

Self-administered Addiction Severity Index (ASI) data were collected on 5,723 patients who received substance abuse treatment in 1 of 110 programs located at 73 Veterans Affairs facilities. The associations between each of three Washington Circle (WC) performance indicator scores (identification, initiation, and engagement) and their casemix-adjusted facility-level improvement in ASI drug and alcohol composites 7 months after intake were estimated. Higher initiation rates were not associated with facility-level improvement in ASI alcohol composite scores but were modestly associated with greater improvements in ASI drug composite scores. Identification and engagement rates were unrelated to 7-month outcomes. WC indicators focused on the early stages of treatment may tap necessary but insufficient processes for patients with substance use disorder to achieve good posttreatment outcomes. Ideally, the WC indicators would be supplemented with other measures of treatment quality.

Demonstrating Improvements from a NWP-based Satellite Precipitation Adjustment Technique in Tropical Mountainous Regions

NASA Astrophysics Data System (ADS)

Zhang, X.; Anagnostou, E. N.

2016-12-01

This research contributes to the improvement of high resolution satellite applications in tropical regions with mountainous topography. Such mountainous regions are usually covered by sparse networks of in-situ observations while quantitative precipitation estimation from satellite sensors exhibits strong underestimation of heavy orographically enhanced storm events. To address this issue, our research applies a satellite error correction technique based solely on high-resolution numerical weather predictions (NWP). Our previous work has demonstrated the accuracy of this method in two mid-latitude mountainous regions (Zhang et al. 2013*1, Zhang et al. 2016*2), while the current research focuses on a comprehensive evaluation in three topical mountainous regions: Colombia, Peru and Taiwan. In addition, two different satellite precipitation products, NOAA Climate Prediction Center morphing technique (CMORPH) and Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks-Cloud Classification System (PERSIANN-CCS), are considered. The study includes a large number of heavy precipitation events (68 events over the three regions) in the period 2004 to 2012. The NWP-based adjustments of the two satellite products are contrasted to their corresponding gauge-adjusted post-processing products. Preliminary results show that the NWP-based adjusted CMORPH product is consistently improved relative to both original and gauge-adjusted precipitation products for all regions and storms examined. The improvement of PERSIANN-CCS product is less significant and less consistent relative to the CMORPH performance improvements from the NWP-based adjustment. *1Zhang, Xinxuan, Emmanouil N. Anagnostou, Maria Frediani, Stavros Solomos, and George Kallos. "Using NWP simulations in satellite rainfall estimation of heavy precipitation events over mountainous areas." Journal of Hydrometeorology 14, no. 6 (2013): 1844-1858.*2 Zhang, Xinxuan, Emmanouil N. Anagnostou

Variational assimilation of streamflow into operational distributed hydrologic models: effect of spatiotemporal adjustment scale

NASA Astrophysics Data System (ADS)

Lee, H.; Seo, D.-J.; Liu, Y.; Koren, V.; McKee, P.; Corby, R.

2012-01-01

assimilation at any adjustment scale produces streamflow predictions with a spatial correlation structure more consistent with that of streamflow observations. We also describe diagnosing the complexity of the assimilation problem using the spatial correlation information associated with the streamflow process, and discuss the effect of timing errors in a simulated hydrograph on the performance of the data assimilation procedure.

Estimation of mean response via effective balancing score

PubMed Central

Hu, Zonghui; Follmann, Dean A.; Wang, Naisyin

2015-01-01

Summary We introduce effective balancing scores for estimation of the mean response under a missing at random mechanism. Unlike conventional balancing scores, the effective balancing scores are constructed via dimension reduction free of model specification. Three types of effective balancing scores are introduced: those that carry the covariate information about the missingness, the response, or both. They lead to consistent estimation with little or no loss in efficiency. Compared to existing estimators, the effective balancing score based estimator relieves the burden of model specification and is the most robust. It is a near-automatic procedure which is most appealing when high dimensional covariates are involved. We investigate both the asymptotic and the numerical properties, and demonstrate the proposed method in a study on Human Immunodeficiency Virus disease. PMID:25797955

Adjustment of regional regression equations for urban storm-runoff quality using at-site data

USGS Publications Warehouse

Barks, C.S.

1996-01-01

Regional regression equations have been developed to estimate urban storm-runoff loads and mean concentrations using a national data base. Four statistical methods using at-site data to adjust the regional equation predictions were developed to provide better local estimates. The four adjustment procedures are a single-factor adjustment, a regression of the observed data against the predicted values, a regression of the observed values against the predicted values and additional local independent variables, and a weighted combination of a local regression with the regional prediction. Data collected at five representative storm-runoff sites during 22 storms in Little Rock, Arkansas, were used to verify, and, when appropriate, adjust the regional regression equation predictions. Comparison of observed values of stormrunoff loads and mean concentrations to the predicted values from the regional regression equations for nine constituents (chemical oxygen demand, suspended solids, total nitrogen as N, total ammonia plus organic nitrogen as N, total phosphorus as P, dissolved phosphorus as P, total recoverable copper, total recoverable lead, and total recoverable zinc) showed large prediction errors ranging from 63 percent to more than several thousand percent. Prediction errors for 6 of the 18 regional regression equations were less than 100 percent and could be considered reasonable for water-quality prediction equations. The regression adjustment procedure was used to adjust five of the regional equation predictions to improve the predictive accuracy. For seven of the regional equations the observed and the predicted values are not significantly correlated. Thus neither the unadjusted regional equations nor any of the adjustments were appropriate. The mean of the observed values was used as a simple estimator when the regional equation predictions and adjusted predictions were not appropriate.

A note on variance estimation in random effects meta-regression.

PubMed

Sidik, Kurex; Jonkman, Jeffrey N

2005-01-01

For random effects meta-regression inference, variance estimation for the parameter estimates is discussed. Because estimated weights are used for meta-regression analysis in practice, the assumed or estimated covariance matrix used in meta-regression is not strictly correct, due to possible errors in estimating the weights. Therefore, this note investigates the use of a robust variance estimation approach for obtaining variances of the parameter estimates in random effects meta-regression inference. This method treats the assumed covariance matrix of the effect measure variables as a working covariance matrix. Using an example of meta-analysis data from clinical trials of a vaccine, the robust variance estimation approach is illustrated in comparison with two other methods of variance estimation. A simulation study is presented, comparing the three methods of variance estimation in terms of bias and coverage probability. We find that, despite the seeming suitability of the robust estimator for random effects meta-regression, the improved variance estimator of Knapp and Hartung (2003) yields the best performance among the three estimators, and thus may provide the best protection against errors in the estimated weights.

Changes in social adjustment with cognitive processing therapy: effects of treatment and association with PTSD symptom change.

PubMed

Monson, Candice M; Macdonald, Alexandra; Vorstenbosch, Valerie; Shnaider, Philippe; Goldstein, Elizabeth S R; Ferrier-Auerbach, Amanda G; Mocciola, Katharine E

2012-10-01

The current study sought to determine if different spheres of social adjustment, social and leisure, family, and work and income improved immediately following a course of cognitive processing therapy (CPT) when compared with those on a waiting list in a sample of 46 U.S. veterans diagnosed with posttraumatic stress disorder (PTSD). We also sought to determine whether changes in different PTSD symptom clusters were associated with changes in these spheres of social adjustment. Overall social adjustment, extended family relationships, and housework completion significantly improved in the CPT versus waiting-list condition, η(2) = .08 to .11. Hierarchical multiple regression analyses revealed that improvements in total clinician-rated PTSD symptoms were associated with improvements in overall social and housework adjustment. When changes in reexperiencing, avoidance, emotional numbing, and hyperarousal were all in the model accounting for changes in total social adjustment, improvements in emotional numbing symptoms were associated with improvements in overall social, extended family, and housework adjustment (β = .38 to .55). In addition, improvements in avoidance symptoms were associated with improvements in housework adjustment (β = .30), but associated with declines in extended family adjustment (β = -.34). Results suggest that it is important to consider the extent to which PTSD treatments effectively reduce specific types of symptoms, particularly emotional numbing and avoidance, to generally improve social adjustment. Copyright © 2012 International Society for Traumatic Stress Studies.

Lipid Adjustment for Chemical Exposures: Accounting for Concomitant Variables

PubMed Central

Li, Daniel; Longnecker, Matthew P.; Dunson, David B.

2013-01-01

Background Some environmental chemical exposures are lipophilic and need to be adjusted by serum lipid levels before data analyses. There are currently various strategies that attempt to account for this problem, but all have their drawbacks. To address such concerns, we propose a new method that uses Box-Cox transformations and a simple Bayesian hierarchical model to adjust for lipophilic chemical exposures. Methods We compared our Box-Cox method to existing methods. We ran simulation studies in which increasing levels of lipid-adjusted chemical exposure did and did not increase the odds of having a disease, and we looked at both single-exposure and multiple-exposures cases. We also analyzed an epidemiology dataset that examined the effects of various chemical exposures on the risk of birth defects. Results Compared with existing methods, our Box-Cox method produced unbiased estimates, good coverage, similar power, and lower type-I error rates. This was the case in both single- and multiple-exposure simulation studies. Results from analysis of the birth-defect data differed from results using existing methods. Conclusion Our Box-Cox method is a novel and intuitive way to account for the lipophilic nature of certain chemical exposures. It addresses some of the problems with existing methods, is easily extendable to multiple exposures, and can be used in any analyses that involve concomitant variables. PMID:24051893

Semiparametric Estimation of Treatment Effect in a Pretest–Posttest Study with Missing Data

PubMed Central

Davidian, Marie; Tsiatis, Anastasios A.; Leon, Selene

2008-01-01

The pretest–posttest study is commonplace in numerous applications. Typically, subjects are randomized to two treatments, and response is measured at baseline, prior to intervention with the randomized treatment (pretest), and at prespecified follow-up time (posttest). Interest focuses on the effect of treatments on the change between mean baseline and follow-up response. Missing posttest response for some subjects is routine, and disregarding missing cases can lead to invalid inference. Despite the popularity of this design, a consensus on an appropriate analysis when no data are missing, let alone for taking into account missing follow-up, does not exist. Under a semiparametric perspective on the pretest–posttest model, in which limited distributional assumptions on pretest or posttest response are made, we show how the theory of Robins, Rotnitzky and Zhao may be used to characterize a class of consistent treatment effect estimators and to identify the efficient estimator in the class. We then describe how the theoretical results translate into practice. The development not only shows how a unified framework for inference in this setting emerges from the Robins, Rotnitzky and Zhao theory, but also provides a review and demonstration of the key aspects of this theory in a familiar context. The results are also relevant to the problem of comparing two treatment means with adjustment for baseline covariates. PMID:19081743

Semiparametric Estimation of Treatment Effect in a Pretest-Posttest Study with Missing Data.

PubMed

Davidian, Marie; Tsiatis, Anastasios A; Leon, Selene

2005-08-01

The pretest-posttest study is commonplace in numerous applications. Typically, subjects are randomized to two treatments, and response is measured at baseline, prior to intervention with the randomized treatment (pretest), and at prespecified follow-up time (posttest). Interest focuses on the effect of treatments on the change between mean baseline and follow-up response. Missing posttest response for some subjects is routine, and disregarding missing cases can lead to invalid inference. Despite the popularity of this design, a consensus on an appropriate analysis when no data are missing, let alone for taking into account missing follow-up, does not exist. Under a semiparametric perspective on the pretest-posttest model, in which limited distributional assumptions on pretest or posttest response are made, we show how the theory of Robins, Rotnitzky and Zhao may be used to characterize a class of consistent treatment effect estimators and to identify the efficient estimator in the class. We then describe how the theoretical results translate into practice. The development not only shows how a unified framework for inference in this setting emerges from the Robins, Rotnitzky and Zhao theory, but also provides a review and demonstration of the key aspects of this theory in a familiar context. The results are also relevant to the problem of comparing two treatment means with adjustment for baseline covariates.

An empiric estimate of the value of life: updating the renal dialysis cost-effectiveness standard.

PubMed

Lee, Chris P; Chertow, Glenn M; Zenios, Stefanos A

2009-01-01

Proposals to make decisions about coverage of new technology by comparing the technology's incremental cost-effectiveness with the traditional benchmark of dialysis imply that the incremental cost-effectiveness ratio of dialysis is seen a proxy for the value of a statistical year of life. The frequently used ratio for dialysis has, however, not been updated to reflect more recently available data on dialysis. We developed a computer simulation model for the end-stage renal disease population and compared cost, life expectancy, and quality adjusted life expectancy of current dialysis practice relative to three less costly alternatives and to no dialysis. We estimated incremental cost-effectiveness ratios for these alternatives relative to the next least costly alternative and no dialysis and analyzed the population distribution of the ratios. Model parameters and costs were estimated using data from the Medicare population and a large integrated health-care delivery system between 1996 and 2003. The sensitivity of results to model assumptions was tested using 38 scenarios of one-way sensitivity analysis, where parameters informing the cost, utility, mortality and morbidity, etc. components of the model were by perturbed +/-50%. The incremental cost-effectiveness ratio of dialysis of current practice relative to the next least costly alternative is on average $129,090 per quality-adjusted life-year (QALY) ($61,294 per year), but its distribution within the population is wide; the interquartile range is $71,890 per QALY, while the 1st and 99th percentiles are $65,496 and $488,360 per QALY, respectively. Higher incremental cost-effectiveness ratios were associated with older age and more comorbid conditions. Sensitivity to model parameters was comparatively small, with most of the scenarios leading to a change of less than 10% in the ratio. The value of a statistical year of life implied by dialysis practice currently averages $129,090 per QALY ($61,294 per year), but

Current Term Enrollment Estimates: Spring 2014

ERIC Educational Resources Information Center

National Student Clearinghouse, 2014

2014-01-01

Current Term Enrollment Estimates, published every December and May by the National Student Clearinghouse Research Center, include national enrollment estimates by institutional sector, state, enrollment intensity, age group, and gender. Enrollment estimates are adjusted for Clearinghouse data coverage rates by institutional sector, state, and…

Current Term Enrollment Estimates: Fall 2014

ERIC Educational Resources Information Center

National Student Clearinghouse, 2014

2014-01-01

Current Term Enrollment Estimates, published every December and May by the National Student Clearinghouse Research Center (NSCRC), include national enrollment estimates by institutional sector, state, enrollment intensity, age group, and gender. Enrollment estimates are adjusted for Clearinghouse data coverage rates by institutional sector, state,…

Estimating the "impact" of out-of-home placement on child well-being: approaching the problem of selection bias.

PubMed

Berger, Lawrence M; Bruch, Sarah K; Johnson, Elizabeth I; James, Sigrid; Rubin, David

2009-01-01

This study used data on 2,453 children aged 4-17 from the National Survey of Child and Adolescent Well-Being and 5 analytic methods that adjust for selection factors to estimate the impact of out-of-home placement on children's cognitive skills and behavior problems. Methods included ordinary least squares (OLS) regressions and residualized change, simple change, difference-in-difference, and fixed effects models. Models were estimated using the full sample and a matched sample generated by propensity scoring. Although results from the unmatched OLS and residualized change models suggested that out-of-home placement is associated with increased child behavior problems, estimates from models that more rigorously adjust for selection bias indicated that placement has little effect on children's cognitive skills or behavior problems.

Colored noise effects on batch attitude accuracy estimates

NASA Technical Reports Server (NTRS)

Bilanow, Stephen

1991-01-01

The effects of colored noise on the accuracy of batch least squares parameter estimates with applications to attitude determination cases are investigated. The standard approaches used for estimating the accuracy of a computed attitude commonly assume uncorrelated (white) measurement noise, while in actual flight experience measurement noise often contains significant time correlations and thus is colored. For example, horizon scanner measurements from low Earth orbit were observed to show correlations over many minutes in response to large scale atmospheric phenomena. A general approach to the analysis of the effects of colored noise is investigated, and interpretation of the resulting equations provides insight into the effects of any particular noise color and the worst case noise coloring for any particular parameter estimate. It is shown that for certain cases, the effects of relatively short term correlations can be accommodated by a simple correction factor. The errors in the predicted accuracy assuming white noise and the reduced accuracy due to the suboptimal nature of estimators that do not take into account the noise color characteristics are discussed. The appearance of a variety of sample noise color characteristics are demonstrated through simulation, and their effects are discussed for sample estimation cases. Based on the analysis, options for dealing with the effects of colored noise are discussed.

Effects of anchoring and adjustment in the evaluation of product pricing.

PubMed

Elaad, Eitan; Sayag, Neta; Ezer, Aliya

2010-08-01

Anchoring and adjustment comprise a heuristic that creates expectations. Two types of anchors were applied on participants' evaluation of products: the price reference of the product (maximum, minimum, or no price reference) and the context in which the products were evaluated (the prestige of the shopping center). Results showed that both factors anchored evaluations of products' value. Context effects were explained by the different expectations of visitors in prestigious (looking for quality) and less prestigious (seeking a bargain) centers.

Estimating the Cost-Effectiveness of One-Time Screening and Treatment for Hepatitis C in Korea

PubMed Central

Kim, Do Young; Han, Kwang-Hyub; Jun, Byungyool; Kim, Tae Hyun; Park, Sohee; Ward, Thomas; Webster, Samantha; McEwan, Phil

2017-01-01

Background and Aims This study aims to investigate the cost-effectiveness of a one-time hepatitis C virus (HCV) screening and treatment program in South Korea where hepatitis B virus (HBV) prevails, in people aged 40–70, compared to current practice (no screening). Methods A published Markov model was used in conjunction with a screening and treatment decision tree to model patient cohorts, aged 40–49, 50–59 and 60–69 years, distributed across chronic hepatitis C (CHC) and compensated cirrhosis (CC) health states (82.5% and 17.5%, respectively). Based on a published seroepidemiology study, HCV prevalence was estimated at 0.60%, 0.80% and 1.53%, respectively. An estimated 71.7% of the population was screened. Post-diagnosis, 39.4% of patients were treated with a newly available all-oral direct-acting antiviral (DAA) regimen over 5 years. Published rates of sustained virologic response, disease management costs, transition rates and utilities were utilised. Results Screening resulted in the identification of 43,635 previously undiagnosed patients across all cohorts. One-time HCV screening and treatment was estimated to be cost-effective across all cohorts; predicted incremental cost-effectiveness ratios ranged from $5,714 to $8,889 per quality-adjusted life year gained. Incremental costs associated with screening, treatment and disease management ranged from $156.47 to $181.85 million USD; lifetime costs-offsets associated with the avoidance of end stage liver disease complications ranged from $51.47 to $57.48 million USD. Conclusions One-time HCV screening and treatment in South Korean people aged 40–70 is likely to be highly cost-effective compared to the current practice of no screening. PMID:28060834

Functional Mixed Effects Model for Small Area Estimation.

PubMed

Maiti, Tapabrata; Sinha, Samiran; Zhong, Ping-Shou

2016-09-01

Functional data analysis has become an important area of research due to its ability of handling high dimensional and complex data structures. However, the development is limited in the context of linear mixed effect models, and in particular, for small area estimation. The linear mixed effect models are the backbone of small area estimation. In this article, we consider area level data, and fit a varying coefficient linear mixed effect model where the varying coefficients are semi-parametrically modeled via B-splines. We propose a method of estimating the fixed effect parameters and consider prediction of random effects that can be implemented using a standard software. For measuring prediction uncertainties, we derive an analytical expression for the mean squared errors, and propose a method of estimating the mean squared errors. The procedure is illustrated via a real data example, and operating characteristics of the method are judged using finite sample simulation studies.

Mind the Gap! A Multilevel Analysis of Factors Related to Variation in Published Cost-Effectiveness Estimates within and between Countries

PubMed Central

Boehler, Christian E. H.; Lord, Joanne

2016-01-01

Background. Published cost-effectiveness estimates can vary considerably, both within and between countries. Despite extensive discussion, little is known empirically about factors relating to these variations. Objectives. To use multilevel statistical modeling to integrate cost-effectiveness estimates from published economic evaluations to investigate potential causes of variation. Methods. Cost-effectiveness studies of statins for cardiovascular disease prevention were identified by systematic review. Estimates of incremental costs and effects were extracted from reported base case, sensitivity, and subgroup analyses, with estimates grouped in studies and in countries. Three bivariate models were developed: a cross-classified model to accommodate data from multinational studies, a hierarchical model with multinational data allocated to a single category at country level, and a hierarchical model excluding multinational data. Covariates at different levels were drawn from a long list of factors suggested in the literature. Results. We found 67 studies reporting 2094 cost-effectiveness estimates relating to 23 countries (6 studies reporting for more than 1 country). Data and study-level covariates included patient characteristics, intervention and comparator cost, and some study methods (e.g., discount rates and time horizon). After adjusting for these factors, the proportion of variation attributable to countries was negligible in the cross-classified model but moderate in the hierarchical models (14%−19% of total variance). Country-level variables that improved the fit of the hierarchical models included measures of income and health care finance, health care resources, and population risks. Conclusions. Our analysis suggested that variability in published cost-effectiveness estimates is related more to differences in study methods than to differences in national context. Multinational studies were associated with much lower country-level variation than single

Mind the Gap! A Multilevel Analysis of Factors Related to Variation in Published Cost-Effectiveness Estimates within and between Countries.

PubMed

Boehler, Christian E H; Lord, Joanne

2016-01-01

Published cost-effectiveness estimates can vary considerably, both within and between countries. Despite extensive discussion, little is known empirically about factors relating to these variations. To use multilevel statistical modeling to integrate cost-effectiveness estimates from published economic evaluations to investigate potential causes of variation. Cost-effectiveness studies of statins for cardiovascular disease prevention were identified by systematic review. Estimates of incremental costs and effects were extracted from reported base case, sensitivity, and subgroup analyses, with estimates grouped in studies and in countries. Three bivariate models were developed: a cross-classified model to accommodate data from multinational studies, a hierarchical model with multinational data allocated to a single category at country level, and a hierarchical model excluding multinational data. Covariates at different levels were drawn from a long list of factors suggested in the literature. We found 67 studies reporting 2094 cost-effectiveness estimates relating to 23 countries (6 studies reporting for more than 1 country). Data and study-level covariates included patient characteristics, intervention and comparator cost, and some study methods (e.g., discount rates and time horizon). After adjusting for these factors, the proportion of variation attributable to countries was negligible in the cross-classified model but moderate in the hierarchical models (14%-19% of total variance). Country-level variables that improved the fit of the hierarchical models included measures of income and health care finance, health care resources, and population risks. Our analysis suggested that variability in published cost-effectiveness estimates is related more to differences in study methods than to differences in national context. Multinational studies were associated with much lower country-level variation than single-country studies. These findings are for a single clinical

[Effects of social support on the adjustment to extracurricular sports activities among junior high school students].

PubMed

Koshi, Ryoko; Sekizawa, Keiko

2009-10-01

This study examined the hypothesis that when students received and/or provided either support for skill improvement or support for interpersonal relations, their overall adjustment level in extracurricular activities would be higher than for students who received and/or provided neither support. Data were analyzed from 475 junior high school students (female 175, male 300) who were taking extracurricular sports activities, out of 743 research participants. The results were as follows. Students who received support mainly for skill improvement showed a statistically equivalent adjustment level as students who received support mainly for interpersonal relations. Students who received either support showed higher adjustment levels than students who received neither. Additionally, providing support showed the same results. The exchange of different types of social support showed equivalent effects on the adjustment level as the exchange of the same type of social support. These results suggest that even though the types of social support are different for skill improvement or interpersonal relations, the exchange of support positively contributes to junior high school students' adjustment level in extracurricular activities.

Continuous adjustment of threshold voltage in carbon nanotube field-effect transistors through gate engineering

NASA Astrophysics Data System (ADS)

Zhong, Donglai; Zhao, Chenyi; Liu, Lijun; Zhang, Zhiyong; Peng, Lian-Mao

2018-04-01

In this letter, we report a gate engineering method to adjust threshold voltage of carbon nanotube (CNT) based field-effect transistors (FETs) continuously in a wide range, which makes the application of CNT FETs especially in digital integrated circuits (ICs) easier. Top-gated FETs are fabricated using solution-processed CNT network films with stacking Pd and Sc films as gate electrodes. By decreasing the thickness of the lower layer metal (Pd) from 20 nm to zero, the effective work function of the gate decreases, thus tuning the threshold voltage (Vt) of CNT FETs from -1.0 V to 0.2 V. The continuous adjustment of threshold voltage through gate engineering lays a solid foundation for multi-threshold technology in CNT based ICs, which then can simultaneously provide high performance and low power circuit modules on one chip.

HIV quality report cards: impact of case-mix adjustment and statistical methods.

PubMed

Ohl, Michael E; Richardson, Kelly K; Goto, Michihiko; Vaughan-Sarrazin, Mary; Schweizer, Marin L; Perencevich, Eli N

2014-10-15

There will be increasing pressure to publicly report and rank the performance of healthcare systems on human immunodeficiency virus (HIV) quality measures. To inform discussion of public reporting, we evaluated the influence of case-mix adjustment when ranking individual care systems on the viral control quality measure. We used data from the Veterans Health Administration (VHA) HIV Clinical Case Registry and administrative databases to estimate case-mix adjusted viral control for 91 local systems caring for 12 368 patients. We compared results using 2 adjustment methods, the observed-to-expected estimator and the risk-standardized ratio. Overall, 10 913 patients (88.2%) achieved viral control (viral load ≤400 copies/mL). Prior to case-mix adjustment, system-level viral control ranged from 51% to 100%. Seventeen (19%) systems were labeled as low outliers (performance significantly below the overall mean) and 11 (12%) as high outliers. Adjustment for case mix (patient demographics, comorbidity, CD4 nadir, time on therapy, and income from VHA administrative databases) reduced the number of low outliers by approximately one-third, but results differed by method. The adjustment model had moderate discrimination (c statistic = 0.66), suggesting potential for unadjusted risk when using administrative data to measure case mix. Case-mix adjustment affects rankings of care systems on the viral control quality measure. Given the sensitivity of rankings to selection of case-mix adjustment methods-and potential for unadjusted risk when using variables limited to current administrative databases-the HIV care community should explore optimal methods for case-mix adjustment before moving forward with public reporting. Published by Oxford University Press on behalf of the Infectious Diseases Society of America 2014. This work is written by (a) US Government employee(s) and is in the public domain in the US.

Understanding Treatment Effect Estimates When Treatment Effects Are Heterogeneous for More Than One Outcome.

PubMed

Brooks, John M; Chapman, Cole G; Schroeder, Mary C

2018-06-01

Patient-centred care requires evidence of treatment effects across many outcomes. Outcomes can be beneficial (e.g. increased survival or cure rates) or detrimental (e.g. adverse events, pain associated with treatment, treatment costs, time required for treatment). Treatment effects may also be heterogeneous across outcomes and across patients. Randomized controlled trials are usually insufficient to supply evidence across outcomes. Observational data analysis is an alternative, with the caveat that the treatments observed are choices. Real-world treatment choice often involves complex assessment of expected effects across the array of outcomes. Failure to account for this complexity when interpreting treatment effect estimates could lead to clinical and policy mistakes. Our objective was to assess the properties of treatment effect estimates based on choice when treatments have heterogeneous effects on both beneficial and detrimental outcomes across patients. Simulation methods were used to highlight the sensitivity of treatment effect estimates to the distributions of treatment effects across patients across outcomes. Scenarios with alternative correlations between benefit and detriment treatment effects across patients were used. Regression and instrumental variable estimators were applied to the simulated data for both outcomes. True treatment effect parameters are sensitive to the relationships of treatment effectiveness across outcomes in each study population. In each simulation scenario, treatment effect estimate interpretations for each outcome are aligned with results shown previously in single outcome models, but these estimates vary across simulated populations with the correlations of treatment effects across patients across outcomes. If estimator assumptions are valid, estimates across outcomes can be used to assess the optimality of treatment rates in a study population. However, because true treatment effect parameters are sensitive to correlations

Supersensitive ancilla-based adaptive quantum phase estimation

NASA Astrophysics Data System (ADS)

Larson, Walker; Saleh, Bahaa E. A.

2017-10-01

The supersensitivity attained in quantum phase estimation is known to be compromised in the presence of decoherence. This is particularly patent at blind spots—phase values at which sensitivity is totally lost. One remedy is to use a precisely known reference phase to shift the operation point to a less vulnerable phase value. Since this is not always feasible, we present here an alternative approach based on combining the probe with an ancillary degree of freedom containing adjustable parameters to create an entangled quantum state of higher dimension. We validate this concept by simulating a configuration of a Mach-Zehnder interferometer with a two-photon probe and a polarization ancilla of adjustable parameters, entangled at a polarizing beam splitter. At the interferometer output, the photons are measured after an adjustable unitary transformation in the polarization subspace. Through calculation of the Fisher information and simulation of an estimation procedure, we show that optimizing the adjustable polarization parameters using an adaptive measurement process provides globally supersensitive unbiased phase estimates for a range of decoherence levels, without prior information or a reference phase.

Worksheets for computing recommended notebook computer and workstation adjustments.

PubMed

Nanthavanij, Suebsak; Udomratana, Chatkate; Hansawad, Saowalak; Thepkanjana, Jayaporn; Tantasuwan, Wanchalerm

2013-01-01

This paper discusses the design and development of worksheets for helping notebook computer (NBC) users to compute NBC and workstation adjustments so as to assume an appropriate seated posture. The worksheets (one for male users, the other for female ones) require the following information: body height, NBC screen size, work surface height, and seat height. The worksheets contain tables for estimating recommended NBC base angle, NBC screen angle, body-NBC distance, work surface height, and seat height. Additionally, they include flow charts to help NBC users to determine necessary adjustment accessories and their settings.

The Effect of Family Communication Patterns on Adopted Adolescent Adjustment

ERIC Educational Resources Information Center

Rueter, Martha A.; Koerner, Ascan F.

2008-01-01

Adoption and family communication both affect adolescent adjustment. We proposed that adoption status and family communication interact such that adopted adolescents in families with certain communication patterns are at greater risk for adjustment problems. We tested this hypothesis using a community-based sample of 384 adoptive and 208…

Joint inversion estimate of regional glacial isostatic adjustment in Antarctica considering a lateral varying Earth structure (ESA STSE Project REGINA)

NASA Astrophysics Data System (ADS)

Sasgen, Ingo; Martín-Español, Alba; Horvath, Alexander; Klemann, Volker; Petrie, Elizabeth J.; Wouters, Bert; Horwath, Martin; Pail, Roland; Bamber, Jonathan L.; Clarke, Peter J.; Konrad, Hannes; Drinkwater, Mark R.

2017-12-01

A major uncertainty in determining the mass balance of the Antarctic ice sheet from measurements of satellite gravimetry, and to a lesser extent satellite altimetry, is the poorly known correction for the ongoing deformation of the solid Earth caused by glacial isostatic adjustment (GIA). Although much progress has been made in consistently modeling the ice-sheet evolution throughout the last glacial cycle, as well as the induced bedrock deformation caused by these load changes, forward models of GIA remain ambiguous due to the lack of observational constraints on the ice sheet's past extent and thickness and mantle rheology beneath the continent. As an alternative to forward-modeling GIA, we estimate GIA from multiple space-geodetic observations: Gravity Recovery and Climate Experiment (GRACE), Envisat/ICESat and Global Positioning System (GPS). Making use of the different sensitivities of the respective satellite observations to current and past surface-mass (ice mass) change and solid Earth processes, we estimate GIA based on viscoelastic response functions to disc load forcing. We calculate and distribute the viscoelastic response functions according to estimates of the variability of lithosphere thickness and mantle viscosity in Antarctica. We compare our GIA estimate with published GIA corrections and evaluate its impact in determining the ice-mass balance in Antarctica from GRACE and satellite altimetry. Particular focus is applied to the Amundsen Sea Sector in West Antarctica, where uplift rates of several centimetres per year have been measured by GPS. We show that most of this uplift is caused by the rapid viscoelastic response to recent ice-load changes, enabled by the presence of a low-viscosity upper mantle in West Antarctica. This paper presents the second and final contributions summarizing the work carried out within a European Space Agency funded study, REGINA (www.regina-science.eu).

38 CFR 18.444 - Academic adjustments.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 38 Pensions, Bonuses, and Veterans' Relief 2 2013-07-01 2013-07-01 false Academic adjustments. 18....444 Academic adjustments. (a) Academic requirements. A recipient shall make necessary modifications to its academic requirements to ensure that these requirements do not discriminate or have the effect of...

38 CFR 18.444 - Academic adjustments.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 38 Pensions, Bonuses, and Veterans' Relief 2 2014-07-01 2014-07-01 false Academic adjustments. 18....444 Academic adjustments. (a) Academic requirements. A recipient shall make necessary modifications to its academic requirements to ensure that these requirements do not discriminate or have the effect of...

38 CFR 18.444 - Academic adjustments.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 38 Pensions, Bonuses, and Veterans' Relief 2 2012-07-01 2012-07-01 false Academic adjustments. 18....444 Academic adjustments. (a) Academic requirements. A recipient shall make necessary modifications to its academic requirements to ensure that these requirements do not discriminate or have the effect of...

38 CFR 18.444 - Academic adjustments.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 38 Pensions, Bonuses, and Veterans' Relief 2 2011-07-01 2011-07-01 false Academic adjustments. 18....444 Academic adjustments. (a) Academic requirements. A recipient shall make necessary modifications to its academic requirements to ensure that these requirements do not discriminate or have the effect of...

Adolescent adjustment and well-being: effects of parental divorce and distress.

PubMed

Størksen, Ingunn; Røysamb, Espen; Holmen, Turid L; Tambs, Kristian

2006-02-01

This study investigates the long-term effects of parental divorce on adolescent psychological adjustment and well-being, and to what extent the effects are accounted for by parental psychological distress. Data were collected among 8,984 Norwegian adolescents (13-19 years) and their parents. Outcome variables were symptoms of anxiety and depression, subjective well-being, and three areas of school problems. Parental divorce was found to be associated with both higher mean levels and larger variances in adolescent problems. Divorce and parental distress contributed independently to adolescent distress, supporting the notion of "double exposure" effects. The prevalence of adolescents with substantial distress symptoms was 14% among those with non-distressed non-divorced parents and 30% among those with divorced and distressed parents. In general effects remained when controlling for demographic factors. Long-term effects of divorce on symptoms of anxiety and depression were stronger among girls than among boys.

Efficacy of a numerical value of a fixed-effect estimator in stochastic frontier analysis as an indicator of hospital production structure.

PubMed

Kawaguchi, Hiroyuki; Hashimoto, Hideki; Matsuda, Shinya

2012-09-22

The casemix-based payment system has been adopted in many countries, although it often needs complementary adjustment taking account of each hospital's unique production structure such as teaching and research duties, and non-profit motives. It has been challenging to numerically evaluate the impact of such structural heterogeneity on production, separately of production inefficiency. The current study adopted stochastic frontier analysis and proposed a method to assess unique components of hospital production structures using a fixed-effect variable. There were two stages of analyses in this study. In the first stage, we estimated the efficiency score from the hospital production function using a true fixed-effect model (TFEM) in stochastic frontier analysis. The use of a TFEM allowed us to differentiate the unobserved heterogeneity of individual hospitals as hospital-specific fixed effects. In the second stage, we regressed the obtained fixed-effect variable for structural components of hospitals to test whether the variable was explicitly related to the characteristics and local disadvantages of the hospitals. In the first analysis, the estimated efficiency score was approximately 0.6. The mean value of the fixed-effect estimator was 0.784, the standard deviation was 0.137, the range was between 0.437 and 1.212. The second-stage regression confirmed that the value of the fixed effect was significantly correlated with advanced technology and local conditions of the sample hospitals. The obtained fixed-effect estimator may reflect hospitals' unique structures of production, considering production inefficiency. The values of fixed-effect estimators can be used as evaluation tools to improve fairness in the reimbursement system for various functions of hospitals based on casemix classification.

A novel measure of effect size for mediation analysis.

PubMed

Lachowicz, Mark J; Preacher, Kristopher J; Kelley, Ken

2018-06-01

Mediation analysis has become one of the most popular statistical methods in the social sciences. However, many currently available effect size measures for mediation have limitations that restrict their use to specific mediation models. In this article, we develop a measure of effect size that addresses these limitations. We show how modification of a currently existing effect size measure results in a novel effect size measure with many desirable properties. We also derive an expression for the bias of the sample estimator for the proposed effect size measure and propose an adjusted version of the estimator. We present a Monte Carlo simulation study conducted to examine the finite sampling properties of the adjusted and unadjusted estimators, which shows that the adjusted estimator is effective at recovering the true value it estimates. Finally, we demonstrate the use of the effect size measure with an empirical example. We provide freely available software so that researchers can immediately implement the methods we discuss. Our developments here extend the existing literature on effect sizes and mediation by developing a potentially useful method of communicating the magnitude of mediation. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Is Weight-Based Adjustment of Automatic Exposure Control Necessary for the Reduction of Chest CT Radiation Dose?

PubMed Central

Prakash, Priyanka; Gilman, Matthew D.; Shepard, Jo-Anne O.; Digumarthy, Subba R.

2010-01-01

Objective To assess the effects of radiation dose reduction in the chest CT using a weight-based adjustment of the automatic exposure control (AEC) technique. Materials and Methods With Institutional Review Board Approval, 60 patients (mean age, 59.1 years; M:F = 35:25) and 57 weight-matched patients (mean age, 52.3 years, M:F = 25:32) were scanned using a weight-adjusted AEC and non-weight-adjusted AEC, respectively on a 64-slice multidetector CT with a 0.984:1 pitch, 0.5 second rotation time, 40 mm table feed/rotation, and 2.5 mm section thickness. Patients were categorized into 3 weight categories; < 60 kg (n = 17), 60-90 kg (n = 52), and > 90 kg (n = 48). Patient weights, scanning parameters, CT dose index volumes (CTDIvol) and dose length product (DLP) were recorded, while effective dose (ED) was estimated. Image noise was measured in the descending thoracic aorta. Data were analyzed using a standard statistical package (SAS/STAT) (Version 9.1, SAS institute Inc, Cary, NC). Results Compared to the non-weight-adjusted AEC, the weight-adjusted AEC technique resulted in an average decrease of 29% in CTDIvol and a 27% effective dose reduction (p < 0.0001). With weight-adjusted AEC, the CTDIvol decreased to 15.8, 15.9, and 27.3 mGy for the < 60, 60-90 and > 91 kg weight groups, respectively, compared to 20.3, 27.9 and 32.8 mGy, with non-weight-adjusted AEC. No significant difference was observed for objective image noise between the chest CT acquired with the non-weight-adjusted (15.0 ± 3.1) and weight-adjusted (16.1 ± 5.6) AEC techniques (p > 0.05). Conclusion The results of this study suggest that AEC should be tailored according to patient weight. Without weight-based adjustment of AEC, patients are exposed to a 17 - 43% higher radiation-dose from a chest CT. PMID:20046494

Frontier production function estimates for steam electric generation: a comparative analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kopp, R.J.; Smith, V.K.

1980-04-01

The performance of three frontier steam electric generation estimators is compared in terms of the consideration given to new production technologies and their technical efficiency. The Cobb-Douglas, constant elasticity of substitution, and translog production functions are examined, using the Aigner-Chu linear programming, the sophisticated Aigner-Lovell-Schmidt stochastic frontier, and the direct method of adjusted ordinary least squares frontier estimators. The use of Cobb-Douglas specification is judged to have narrowed the perceived difference between competing estimators. The choice of frontier estimator is concluded to have a greater effect on the plant efficiency than functional form. 19 references. (DCK)

A review of statistical estimators for risk-adjusted length of stay: analysis of the Australian and new Zealand Intensive Care Adult Patient Data-Base, 2008-2009.

PubMed

Moran, John L; Solomon, Patricia J

2012-05-16

For the analysis of length-of-stay (LOS) data, which is characteristically right-skewed, a number of statistical estimators have been proposed as alternatives to the traditional ordinary least squares (OLS) regression with log dependent variable. Using a cohort of patients identified in the Australian and New Zealand Intensive Care Society Adult Patient Database, 2008-2009, 12 different methods were used for estimation of intensive care (ICU) length of stay. These encompassed risk-adjusted regression analysis of firstly: log LOS using OLS, linear mixed model [LMM], treatment effects, skew-normal and skew-t models; and secondly: unmodified (raw) LOS via OLS, generalised linear models [GLMs] with log-link and 4 different distributions [Poisson, gamma, negative binomial and inverse-Gaussian], extended estimating equations [EEE] and a finite mixture model including a gamma distribution. A fixed covariate list and ICU-site clustering with robust variance were utilised for model fitting with split-sample determination (80%) and validation (20%) data sets, and model simulation was undertaken to establish over-fitting (Copas test). Indices of model specification using Bayesian information criterion [BIC: lower values preferred] and residual analysis as well as predictive performance (R2, concordance correlation coefficient (CCC), mean absolute error [MAE]) were established for each estimator. The data-set consisted of 111663 patients from 131 ICUs; with mean(SD) age 60.6(18.8) years, 43.0% were female, 40.7% were mechanically ventilated and ICU mortality was 7.8%. ICU length-of-stay was 3.4(5.1) (median 1.8, range (0.17-60)) days and demonstrated marked kurtosis and right skew (29.4 and 4.4 respectively). BIC showed considerable spread, from a maximum of 509801 (OLS-raw scale) to a minimum of 210286 (LMM). R2 ranged from 0.22 (LMM) to 0.17 and the CCC from 0.334 (LMM) to 0.149, with MAE 2.2-2.4. Superior residual behaviour was established for the log-scale estimators

Estimating linear effects in ANOVA designs: the easy way.

PubMed

Pinhas, Michal; Tzelgov, Joseph; Ganor-Stern, Dana

2012-09-01

Research in cognitive science has documented numerous phenomena that are approximated by linear relationships. In the domain of numerical cognition, the use of linear regression for estimating linear effects (e.g., distance and SNARC effects) became common following Fias, Brysbaert, Geypens, and d'Ydewalle's (1996) study on the SNARC effect. While their work has become the model for analyzing linear effects in the field, it requires statistical analysis of individual participants and does not provide measures of the proportions of variability accounted for (cf. Lorch & Myers, 1990). In the present methodological note, using both the distance and SNARC effects as examples, we demonstrate how linear effects can be estimated in a simple way within the framework of repeated measures analysis of variance. This method allows for estimating effect sizes in terms of both slope and proportions of variability accounted for. Finally, we show that our method can easily be extended to estimate linear interaction effects, not just linear effects calculated as main effects.

Adjusting for treatment effects in studies of quantitative traits: antihypertensive therapy and systolic blood pressure.

PubMed

Tobin, Martin D; Sheehan, Nuala A; Scurrah, Katrina J; Burton, Paul R

2005-10-15

A population-based study of a quantitative trait may be seriously compromised when the trait is subject to the effects of a treatment. For example, in a typical study of quantitative blood pressure (BP) 15 per cent or more of middle-aged subjects may take antihypertensive treatment. Without appropriate correction, this can lead to substantial shrinkage in the estimated effect of aetiological determinants of scientific interest and a marked reduction in statistical power. Correction relies upon imputation, in treated subjects, of the underlying BP from the observed BP having invoked one or more assumptions about the bioclinical setting. There is a range of different assumptions that may be made, and a number of different analytical models that may be used. In this paper, we motivate an approach based on a censored normal regression model and compare it with a range of other methods that are currently used or advocated. We compare these methods in simulated data sets and assess the estimation bias and the loss of power that ensue when treatment effects are not appropriately addressed. We also apply the same methods to real data and demonstrate a pattern of behaviour that is consistent with that in the simulation studies. Although all approaches to analysis are necessarily approximations, we conclude that two of the adjustment methods appear to perform well across a range of realistic settings. These are: (1) the addition of a sensible constant to the observed BP in treated subjects; and (2) the censored normal regression model. A third, non-parametric, method based on averaging ordered residuals may also be advocated in some settings. On the other hand, three approaches that are used relatively commonly are fundamentally flawed and should not be used at all. These are: (i) ignoring the problem altogether and analysing observed BP in treated subjects as if it was underlying BP; (ii) fitting a conventional regression model with treatment as a binary covariate; and (iii

Impact of particulate air pollution on quality-adjusted life expectancy in Canada.

PubMed

Coyle, Douglas; Stieb, Dave; Burnett, Richard T; DeCivita, Paul; Krewski, Daniel; Chen, Yue; Thun, Michael J

Air pollution and premature death are important public health concerns. Analyses have repeatedly demonstrated that airborne particles are associated with increased mortality and estimates have been used to forecast the impact on life expectancy. In this analysis, we draw upon data from the American Cancer Society (ACS) cohort and literature on utility-based measures of quality of life in relation to health status to more fully quantify the effects of air pollution on mortality in terms of quality-adjusted life expectancy. The analysis was conducted within a decision analytic model using Monte Carlo simulation techniques. Outcomes were estimated based on projections of the Canadian population. A one-unit reduction in sulfate air pollution would yield a mean annual increase in Quality-Adjusted Life Years (QALYs) of 20,960, with gains being greater for individuals with lower educational status and for males compared to females. This suggests that the impact of reductions in sulfate air pollution on quality-adjusted life expectancy is substantial. Interpretation of the results is unclear. However, the potential gains in QALYs from reduced air pollutants can be contrasted to the costs of policies to bring about such reductions. Based on a tentative threshold for the value of health benefits, analysis suggests that an investment in Canada of over 1 billion dollars per annum would be an efficient use of resources if it could be demonstrated that this would reduce sulfate concentrations in ambient air by 1 microg/m(3). Further analysis can assess the efficiency of targeting such initiatives to communities that are most likely to benefit.

Joint nonparametric correction estimator for excess relative risk regression in survival analysis with exposure measurement error

PubMed Central

Wang, Ching-Yun; Cullings, Harry; Song, Xiao; Kopecky, Kenneth J.

2017-01-01

SUMMARY Observational epidemiological studies often confront the problem of estimating exposure-disease relationships when the exposure is not measured exactly. In the paper, we investigate exposure measurement error in excess relative risk regression, which is a widely used model in radiation exposure effect research. In the study cohort, a surrogate variable is available for the true unobserved exposure variable. The surrogate variable satisfies a generalized version of the classical additive measurement error model, but it may or may not have repeated measurements. In addition, an instrumental variable is available for individuals in a subset of the whole cohort. We develop a nonparametric correction (NPC) estimator using data from the subcohort, and further propose a joint nonparametric correction (JNPC) estimator using all observed data to adjust for exposure measurement error. An optimal linear combination estimator of JNPC and NPC is further developed. The proposed estimators are nonparametric, which are consistent without imposing a covariate or error distribution, and are robust to heteroscedastic errors. Finite sample performance is examined via a simulation study. We apply the developed methods to data from the Radiation Effects Research Foundation, in which chromosome aberration is used to adjust for the effects of radiation dose measurement error on the estimation of radiation dose responses. PMID:29354018

Medicare spending by state: the border-crossing adjustment.

PubMed

Basu, J; Lazenby, H C; Levit, K R

1995-01-01

As the first step in a pioneering effort by the Health Care Financing Administration (HCFA) to measure interstate border crossing for services used by both Medicare and non-Medicare beneficiaries, the authors study the spending behavior of Medicare beneficiaries for 10 Medicare-covered services. Based on interstate flow-of-expenditure data developed for calendar year 1991, the authors analyze the spending patterns of State residents by studying the inflow and outflow rates and the netflow ratios of expenditures incurred by Medicare patients. The report also provides per capita expenditure estimates with residence-based adjustments and evaluates the impact of the border-crossing adjustment for individual services and States.

The additive and interactive effects of parenting and temperament in predicting adjustment problems of children of divorce.

PubMed

Lengua, L J; Wolchik, S A; Sandler, I N; West, S G

2000-06-01

Investigated the interaction between parenting and temperament in predicting adjustment problems in children of divorce. The study utilized a sample of 231 mothers and children, 9 to 12 years old, who had experienced divorce within the previous 2 years. Both mothers' and children's reports on parenting, temperament, and adjustment variables were obtained and combined to create cross-reporter measures of the variables. Parenting and temperament were directly and independently related to outcomes consistent with an additive model of their effects. Significant interactions indicated that parental rejection was more strongly related to adjustment problems for children low in positive emotionality, and inconsistent discipline was more strongly related to adjustment problems for children high in impulsivity. These findings suggest that children who are high in impulsivity may be at greater risk for developing problems, whereas positive emotionality may operate as a protective factor, decreasing the risk of adjustment problems in response to negative parenting.

Using chronic disease risk factors to adjust Medicare capitation payments

PubMed Central

Schauffler, Helen Halpin; Howland, Jonathan; Cobb, Janet

1992-01-01

This study evaluates the use of risk factors for chronic disease as health status adjusters for Medicare's capitation formula, the average adjusted per capita costs (AAPCC). Risk factor data for the surviving members of the Framingham Study cohort who were examined in 1982-83 were merged with 100 percent Medicare payment data for 1984 and 1985, matching on Social Security number and sex. Seven different AAPCC models were estimated to assess the independent contributions of risk factors and measures of prior utilization and disability in increasing the explanatory power of AAPCC. The findings suggest that inclusion of risk factors for chronic disease as health status adjusters can improve substantially the predictive accuracy of AAPCC. PMID:10124441

Two-step estimation in ratio-of-mediator-probability weighted causal mediation analysis.

PubMed

Bein, Edward; Deutsch, Jonah; Hong, Guanglei; Porter, Kristin E; Qin, Xu; Yang, Cheng

2018-04-15

This study investigates appropriate estimation of estimator variability in the context of causal mediation analysis that employs propensity score-based weighting. Such an analysis decomposes the total effect of a treatment on the outcome into an indirect effect transmitted through a focal mediator and a direct effect bypassing the mediator. Ratio-of-mediator-probability weighting estimates these causal effects by adjusting for the confounding impact of a large number of pretreatment covariates through propensity score-based weighting. In step 1, a propensity score model is estimated. In step 2, the causal effects of interest are estimated using weights derived from the prior step's regression coefficient estimates. Statistical inferences obtained from this 2-step estimation procedure are potentially problematic if the estimated standard errors of the causal effect estimates do not reflect the sampling uncertainty in the estimation of the weights. This study extends to ratio-of-mediator-probability weighting analysis a solution to the 2-step estimation problem by stacking the score functions from both steps. We derive the asymptotic variance-covariance matrix for the indirect effect and direct effect 2-step estimators, provide simulation results, and illustrate with an application study. Our simulation results indicate that the sampling uncertainty in the estimated weights should not be ignored. The standard error estimation using the stacking procedure offers a viable alternative to bootstrap standard error estimation. We discuss broad implications of this approach for causal analysis involving propensity score-based weighting. Copyright © 2018 John Wiley & Sons, Ltd.

Assessment of Patient-Specific Surgery Effect Based on Weighted Estimation and Propensity Scoring in the Re-Analysis of the Sciatica Trial

PubMed Central

Mertens, Bart J. A.; Jacobs, Wilco C. H.; Brand, Ronald; Peul, Wilco C.

2014-01-01

We consider a re-analysis of the wait-and-see (control) arm of a recent clinical trial on sciatica. While the original randomised trial was designed to evaluate the public policy effect of a conservative wait-and-see approach versus early surgery, we investigate the impact of surgery at the individual patient level in a re-analysis of the wait-and-see group data. Both marginal structural model re-weighted estimates as well as propensity score adjusted analyses are presented. Results indicate that patients with high propensity to receive surgery may have beneficial effects at 2 years from delayed disc surgery. PMID:25353633

Light-adjustable lens.

PubMed Central

Schwartz, Daniel M

2003-01-01

PURPOSE: First, to determine whether a silicone light-adjustable intraocular lens (IOL) can be fabricated and adjusted precisely with a light delivery device (LDD). Second, to determine the biocompatibility of an adjustable IOL and whether the lens can be adjusted precisely in vivo. METHODS: After fabrication of a light-adjustable silicone formulation, IOLs were made and tested in vitro for cytotoxicity, leaching, precision of adjustment, optical quality after adjustment, and mechanical properties. Light-adjustable IOLs were then tested in vivo for biocompatibility and precision of adjustment in a rabbit model. In collaboration with Zeiss-Meditec, a digital LDD was developed and tested to correct for higher-order aberrations in light-adjustable IOLs. RESULTS: The results establish that a biocompatible silicone IOL can be fabricated and adjusted using safe levels of light. There was no evidence of cytotoxicity or leaching. Testing of mechanical properties revealed no significant differences from commercial controls. Implantation of light-adjustable lenses in rabbits demonstrated- excellent biocompatibility after 6 months, comparable to a commercially available IOL. In vivo spherical (hyperopic and myopic) adjustment in rabbits was achieved using an analog light delivery system. The digital light delivery system was tested and achieved correction of higher-order aberrations. CONCLUSION: A silicone light-adjustable IOL and LDD have been developed to enable postoperative, noninvasive adjustment of lens power. The ability to correct higher-order aberrations in these materials has broad potential applicability for optimization of vision in patients undergoing cataract and refractive surgery. PMID:14971588

Monitoring low birth weight: an evaluation of international estimates and an updated estimation procedure.

PubMed Central

Blanc, Ann K.; Wardlaw, Tessa

2005-01-01

OBJECTIVE: To critically examine the data used to produce estimates of the proportion of infants with low birth weight in developing countries and to describe biases in these data. To assess the effect of adjustment procedures on the estimates and propose a modified estimation procedure for international reporting purposes. METHODS: Mothers' reports about their recent births in 62 nationally representative Demographic and Health Surveys (DHS) conducted between 1990 and 2000 were analysed. The proportion of infants weighed at birth, characteristics of those weighed, extent of misreporting, and mothers' subjective assessments of their children's size at birth were examined. FINDINGS: In many developing countries the majority of infants were not weighed at birth. Those who were weighed were more likely to have mothers who live in urban areas and are educated, and to be born in a medical facility with assistance from medically trained personnel. Birth weights reported by mothers are "heaped" on multiples of 500 grams. CONCLUSION: Current survey-based estimates of the prevalence of low birth weight are biased substantially downwards. Two adjustments to reported data are recommended: a weighting procedure that combines reported birth weights with mothers' assessment of the child's size at birth, and categorization of one-quarter of the infants reported to have a birth weight of exactly 2500 grams as having low birth weight. Averaged over all surveys, these procedures increased the proportion classified as having low birth weight by 25%. We also recommend that the proportion of infants not weighed at birth be routinely reported. Efforts are needed to increase the weighing of newborns and the recording of their weights. PMID:15798841

Task-related and person-related variables influence the effect of low back pain on anticipatory postural adjustments.

PubMed

Jacobs, Jesse V; Lyman, Courtney A; Hitt, Juvena R; Henry, Sharon M

2017-08-01

People with low back pain exhibit altered postural coordination that has been suggested as a target for treatment, but heterogeneous presentation has rendered it difficult to identify appropriate candidates and protocols for such treatments. This study evaluated the associations of task-related and person-related factors with the effect of low back pain on anticipatory postural adjustments. Thirteen subjects with and 13 without low back pain performed seated, rapid arm flexion in self-initiated and cued conditions. Mixed-model ANOVA were used to evaluate group and condition effects on APA onset latencies of trunk muscles, arm-raise velocity, and pre-movement cortical potentials. These measures were evaluated for correlation with pain ratings, Fear Avoidance Beliefs Questionnaire scores, and Modified Oswestry Questionnaire scores. Delayed postural adjustments of subjects with low back pain were greater in the cued condition than in the self-initiated condition. The group with low back pain exhibited larger-amplitude cortical potentials than the group without pain, but also significantly slower arm-raise velocities. With arm-raise velocity as a covariate, the effect of low back pain remained significant for the latencies of postural adjustments but not for cortical potentials. Latencies of the postural adjustments significantly correlated with Oswestry and Fear Avoidance Beliefs scores. Delayed postural adjustments with low back pain appear to be influenced by cueing of movement, pain-related disability and fear of activity. These results highlight the importance of subject characteristics, task condition, and task performance when comparing across studies or when developing treatment of people with low back pain. Copyright © 2017 Elsevier B.V. All rights reserved.

On-demand Reporting of Risk-adjusted and Smoothed Rates for Quality Profiling in ACS NSQIP.

PubMed

Cohen, Mark E; Liu, Yaoming; Huffman, Kristopher M; Ko, Clifford Y; Hall, Bruce L

2016-12-01

Surgical quality improvement depends on hospitals having accurate and timely information about comparative performance. Profiling accuracy is improved by risk adjustment and shrinkage adjustment to stabilize estimates. These adjustments are included in ACS NSQIP reports, where hospital odds ratios (OR) are estimated using hierarchical models built on contemporaneous data. However, the timeliness of feedback remains an issue. We describe an alternative, nonhierarchical approach, which yields risk- and shrinkage-adjusted rates. In contrast to our "Traditional" NSQIP method, this approach uses preexisting equations, built on historical data, which permits hospitals to have near immediate access to profiling results. We compared our traditional method to this new "on-demand" approach with respect to outlier determinations, kappa statistics, and correlations between logged OR and standardized rates, for 12 models (4 surgical groups by 3 outcomes). When both methods used the same contemporaneous data, there were similar numbers of hospital outliers and correlations between logged OR and standardized rates were high. However, larger differences were observed when the effect of contemporaneous versus historical data was added to differences in statistical methodology. The on-demand, nonhierarchical approach provides results similar to the traditional hierarchical method and offers immediacy, an "over-time" perspective, application to a broader range of models and data subsets, and reporting of more easily understood rates. Although the nonhierarchical method results are now available "on-demand" in a web-based application, the hierarchical approach has advantages, which support its continued periodic publication as the gold standard for hospital profiling in the program.

Assessing risk-adjustment approaches under non-random selection.

PubMed

Luft, Harold S; Dudley, R Adams

2004-01-01

Various approaches have been proposed to adjust for differences in enrollee risk in health plans. Because risk-selection strategies may have different effects on enrollment, we simulated three types of selection--dumping, skimming, and stinting. Concurrent diagnosis-based risk adjustment, and a hybrid using concurrent adjustment for about 8% of the cases and prospective adjustment for the rest, perform markedly better than prospective or demographic adjustments, both in terms of R2 and the extent to which plans experience unwarranted gains or losses. The simulation approach offers a valuable tool for analysts in assessing various risk-adjustment strategies under different selection situations.

RGB-D SLAM Based on Extended Bundle Adjustment with 2D and 3D Information

PubMed Central

Di, Kaichang; Zhao, Qiang; Wan, Wenhui; Wang, Yexin; Gao, Yunjun

2016-01-01

In the study of SLAM problem using an RGB-D camera, depth information and visual information as two types of primary measurement data are rarely tightly coupled during refinement of camera pose estimation. In this paper, a new method of RGB-D camera SLAM is proposed based on extended bundle adjustment with integrated 2D and 3D information on the basis of a new projection model. First, the geometric relationship between the image plane coordinates and the depth values is constructed through RGB-D camera calibration. Then, 2D and 3D feature points are automatically extracted and matched between consecutive frames to build a continuous image network. Finally, extended bundle adjustment based on the new projection model, which takes both image and depth measurements into consideration, is applied to the image network for high-precision pose estimation. Field experiments show that the proposed method has a notably better performance than the traditional method, and the experimental results demonstrate the effectiveness of the proposed method in improving localization accuracy. PMID:27529256

Improved Estimates of Thermodynamic Parameters

NASA Technical Reports Server (NTRS)

Lawson, D. D.

1982-01-01

Techniques refined for estimating heat of vaporization and other parameters from molecular structure. Using parabolic equation with three adjustable parameters, heat of vaporization can be used to estimate boiling point, and vice versa. Boiling points and vapor pressures for some nonpolar liquids were estimated by improved method and compared with previously reported values. Technique for estimating thermodynamic parameters should make it easier for engineers to choose among candidate heat-exchange fluids for thermochemical cycles.

Accounting for missing data in the estimation of contemporary genetic effective population size (N(e) ).

PubMed

Peel, D; Waples, R S; Macbeth, G M; Do, C; Ovenden, J R

2013-03-01

Theoretical models are often applied to population genetic data sets without fully considering the effect of missing data. Researchers can deal with missing data by removing individuals that have failed to yield genotypes and/or by removing loci that have failed to yield allelic determinations, but despite their best efforts, most data sets still contain some missing data. As a consequence, realized sample size differs among loci, and this poses a problem for unbiased methods that must explicitly account for random sampling error. One commonly used solution for the calculation of contemporary effective population size (N(e) ) is to calculate the effective sample size as an unweighted mean or harmonic mean across loci. This is not ideal because it fails to account for the fact that loci with different numbers of alleles have different information content. Here we consider this problem for genetic estimators of contemporary effective population size (N(e) ). To evaluate bias and precision of several statistical approaches for dealing with missing data, we simulated populations with known N(e) and various degrees of missing data. Across all scenarios, one method of correcting for missing data (fixed-inverse variance-weighted harmonic mean) consistently performed the best for both single-sample and two-sample (temporal) methods of estimating N(e) and outperformed some methods currently in widespread use. The approach adopted here may be a starting point to adjust other population genetics methods that include per-locus sample size components. © 2012 Blackwell Publishing Ltd.

Career Issues and International Adjustment of Business Expatriates.

ERIC Educational Resources Information Center

Selmer, Jan

1999-01-01

A survey of 343 Western business executives working in Hong Kong showed that meeting career goals within the organization did not significantly affect work adjustment but positively affected sociocultural and psychological adjustment. Other career issues (wrong/right career move, and supportive corporate attitudes) had no effect on adjustment. (SK)

Estimating and Testing Mediation Effects with Censored Data

ERIC Educational Resources Information Center

Wang, Lijuan; Zhang, Zhiyong

2011-01-01

This study investigated influences of censored data on mediation analysis. Mediation effect estimates can be biased and inefficient with censoring on any one of the input, mediation, and output variables. A Bayesian Tobit approach was introduced to estimate and test mediation effects with censored data. Simulation results showed that the Bayesian…

Dynamic probability control limits for risk-adjusted CUSUM charts based on multiresponses.

PubMed

Zhang, Xiang; Loda, Justin B; Woodall, William H

2017-07-20

For a patient who has survived a surgery, there could be several levels of recovery. Thus, it is reasonable to consider more than two outcomes when monitoring surgical outcome quality. The risk-adjusted cumulative sum (CUSUM) chart based on multiresponses has been developed for monitoring a surgical process with three or more outcomes. However, there is a significant effect of varying risk distributions on the in-control performance of the chart when constant control limits are applied. To overcome this disadvantage, we apply the dynamic probability control limits to the risk-adjusted CUSUM charts for multiresponses. The simulation results demonstrate that the in-control performance of the charts with dynamic probability control limits can be controlled for different patient populations because these limits are determined for each specific sequence of patients. Thus, the use of dynamic probability control limits for risk-adjusted CUSUM charts based on multiresponses allows each chart to be designed for the corresponding patient sequence of a surgeon or a hospital and therefore does not require estimating or monitoring the patients' risk distribution. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

Significance of adjusting salt intake by body weight in the evaluation of dietary salt and blood pressure.

PubMed

Hashimoto, Tomomi; Takase, Hiroyuki; Okado, Tateo; Sugiura, Tomonori; Yamashita, Sumiyo; Kimura, Genjiro; Ohte, Nobuyuki; Dohi, Yasuaki

2016-08-01

The close association between dietary salt and hypertension is well established. However, previous studies generally assessed salt intake without adjustment for body weight. Herein, we investigated the significance of body weight-adjusted salt intake in the general population. The present cross-sectional study included 7629 participants from our yearly physical checkup program, and their salt intake was assessed using a spot urine test to estimate 24-hour urinary salt excretion. Total salt intake increased with increasing body weight. Body weight-adjusted salt intake was greater in participants with hypertension than in those without hypertension. Systolic blood pressure, estimated glomerular filtration rate, and urinary albumin were independently correlated with body weight-adjusted salt intake after adjustment for possible cardiovascular risk factors. Excessive body weight-adjusted salt intake could be related to an increase in blood pressure and hypertensive organ damage. Adjustment for body weight might therefore provide clinically important information when assessing individual salt intake. Copyright © 2016 American Society of Hypertension. Published by Elsevier Inc. All rights reserved.

Prediction of WBGT-based clothing adjustment values from evaporative resistance

PubMed Central

BERNARD, Thomas E.; ASHLEY, Candi D.; GARZON, Ximena P.; KIM, Jung-Hyun; COCA, Aitor

2017-01-01

Wet bulb globe temperature (WBGT) index is used by many professionals in combination with metabolic rate and clothing adjustments to assess whether a heat stress exposure is sustainable. The progressive heat stress protocol is a systematic method to prescribe a clothing adjustment value (CAV) from human wear trials, and it also provides an estimate of apparent total evaporative resistance (Re,T,a). It is clear that there is a direct relationship between the two descriptors of clothing thermal effects with diminishing increases in CAV at high Re,T,a. There were data to suggest an interaction of CAV and Re,T,a with relative humidity at high evaporative resistance. Because human trials are expensive, manikin data can reduce the cost by considering the static total evaporative resistance (Re,T,s). In fact, as the static evaporative resistance increases, the CAV increases in a similar fashion as Re,T,a. While the results look promising that Re,T,s can predict CAV, some validation remains, especially for high evaporative resistance. The data only supports air velocities near 0.5 m/s. PMID:29033404

A kinematic model to estimate effective dose of radioactive substances in a human body

NASA Astrophysics Data System (ADS)

Sasaki, S.; Yamada, T.

2013-05-01

The great earthquake occurred in the north-east area in Japan in March 11, 2011. Facility system to control Fukushima Daiichi nuclear power station was completely destroyed by the following giant tsunami. From the damaged reactor containment vessels, an amount of radioactive substances had leaked and diffused in the vicinity of this station. Radiological internal exposure became a serious social issue both in Japan and all over the world. The present study provides an easily understandable, kinematic-based model to estimate the effective dose of radioactive substances in a human body by simplifying the complicated mechanism of metabolism. International Commission on Radiological Protection (ICRP) has developed a sophisticated model, which is well-known as a standard method to calculate the effective dose for radiological protection. However, owing to that ICRP method is fine, it is rather difficult for non-professional people of radiology to gasp the whole images of the movement and the influences of radioactive substances in a human body. Therefore, in the present paper we propose a newly-derived and easily-understandable model to estimate the effective dose. The present method is very similar with the traditional and conventional tank model in hydrology. Ingestion flux of radioactive substances corresponds to rain intensity and the storage of radioactive substances to the water storage in a basin in runoff analysis. The key of the present method is to estimate the energy radiated in the radioactive nuclear disintegration of an atom by using classical theory of β decay and special relativity for various kinds of radioactive atoms. The parameters used in this model are only physical half-time and biological half-time, and there are no operational parameters or coefficients to adjust our theoretical runoff to ICRP. Figure shows the time-varying effective dose with ingestion duration, and we can confirm the validity of our model. The time-varying effective dose with

25 CFR 1000.104 - Can funding amounts negotiated in an AFA be adjusted during the year it is in effect?

Code of Federal Regulations, 2012 CFR

2012-04-01

... during the year it is in effect? Yes, funding amounts negotiated in an AFA may be adjusted under the... 25 Indians 2 2012-04-01 2012-04-01 false Can funding amounts negotiated in an AFA be adjusted during the year it is in effect? 1000.104 Section 1000.104 Indians OFFICE OF THE ASSISTANT SECRETARY...

25 CFR 1000.104 - Can funding amounts negotiated in an AFA be adjusted during the year it is in effect?

Code of Federal Regulations, 2014 CFR

2014-04-01

... during the year it is in effect? Yes, funding amounts negotiated in an AFA may be adjusted under the... 25 Indians 2 2014-04-01 2014-04-01 false Can funding amounts negotiated in an AFA be adjusted during the year it is in effect? 1000.104 Section 1000.104 Indians OFFICE OF THE ASSISTANT SECRETARY...

25 CFR 1000.104 - Can funding amounts negotiated in an AFA be adjusted during the year it is in effect?

Code of Federal Regulations, 2013 CFR

2013-04-01

... during the year it is in effect? Yes, funding amounts negotiated in an AFA may be adjusted under the... 25 Indians 2 2013-04-01 2013-04-01 false Can funding amounts negotiated in an AFA be adjusted during the year it is in effect? 1000.104 Section 1000.104 Indians OFFICE OF THE ASSISTANT SECRETARY...

25 CFR 1000.104 - Can funding amounts negotiated in an AFA be adjusted during the year it is in effect?

Code of Federal Regulations, 2011 CFR

2011-04-01

... during the year it is in effect? Yes, funding amounts negotiated in an AFA may be adjusted under the... 25 Indians 2 2011-04-01 2011-04-01 false Can funding amounts negotiated in an AFA be adjusted during the year it is in effect? 1000.104 Section 1000.104 Indians OFFICE OF THE ASSISTANT SECRETARY...

25 CFR 1000.104 - Can funding amounts negotiated in an AFA be adjusted during the year it is in effect?

Code of Federal Regulations, 2010 CFR

2010-04-01

... during the year it is in effect? Yes, funding amounts negotiated in an AFA may be adjusted under the... 25 Indians 2 2010-04-01 2010-04-01 false Can funding amounts negotiated in an AFA be adjusted during the year it is in effect? 1000.104 Section 1000.104 Indians OFFICE OF THE ASSISTANT SECRETARY...

Ripcord adjustable suture technique for use in strabismus surgery.

PubMed

Coats, D K

2001-09-01

Adjustable sutures in strabismus surgery may be difficult or impossible in poorly cooperative patients. An adjunct suture technique that allows a 1-step, all-or-nothing, preprogrammed adjustment in patients not considered good candidates for standard postoperative adjustable sutures is described. Twelve patients underwent adjustable strabismus surgery using the ripcord technique. Six patients had unacceptable alignment after surgery. In 5 of these, alignment was successfully adjusted. The ripcord adjustable suture technique is effective and is well tolerated by patients.

Methods for the estimation of the National Institute for Health and Care Excellence cost-effectiveness threshold.

PubMed

Claxton, Karl; Martin, Steve; Soares, Marta; Rice, Nigel; Spackman, Eldon; Hinde, Sebastian; Devlin, Nancy; Smith, Peter C; Sculpher, Mark

2015-02-01

Cost-effectiveness analysis involves the comparison of the incremental cost-effectiveness ratio of a new technology, which is more costly than existing alternatives, with the cost-effectiveness threshold. This indicates whether or not the health expected to be gained from its use exceeds the health expected to be lost elsewhere as other health-care activities are displaced. The threshold therefore represents the additional cost that has to be imposed on the system to forgo 1 quality-adjusted life-year (QALY) of health through displacement. There are no empirical estimates of the cost-effectiveness threshold used by the National Institute for Health and Care Excellence. (1) To provide a conceptual framework to define the cost-effectiveness threshold and to provide the basis for its empirical estimation. (2) Using programme budgeting data for the English NHS, to estimate the relationship between changes in overall NHS expenditure and changes in mortality. (3) To extend this mortality measure of the health effects of a change in expenditure to life-years and to QALYs by estimating the quality-of-life (QoL) associated with effects on years of life and the additional direct impact on QoL itself. (4) To present the best estimate of the cost-effectiveness threshold for policy purposes. Earlier econometric analysis estimated the relationship between differences in primary care trust (PCT) spending, across programme budget categories (PBCs), and associated disease-specific mortality. This research is extended in several ways including estimating the impact of marginal increases or decreases in overall NHS expenditure on spending in each of the 23 PBCs. Further stages of work link the econometrics to broader health effects in terms of QALYs. The most relevant 'central' threshold is estimated to be £12,936 per QALY (2008 expenditure, 2008-10 mortality). Uncertainty analysis indicates that the probability that the threshold is < £20,000 per QALY is 0.89 and the probability

Teachers and Their International Relocation: The Effect of Self-Esteem and Pay Satisfaction on Adjustment and Outcome Variables

ERIC Educational Resources Information Center

Richardson, Warnie; von Kirchenheim, Clement; Richardson, Carole

2006-01-01

This is the second of two papers investigating the adjustment process in a designated group of expatriates, (teachers), who have severed ties with their home country and employer. In the first paper we examined the effect of self-efficacy and flexibility within this adjustment process, revealing the significance of self-efficacy but failing to…

Acculturation, personality, and psychological adjustment.

PubMed

Ahadi, Stephan A; Puente-Díaz, Rogelio

2011-12-01

Two studies investigated relationships between traditional indicators of acculturation, cultural distance, acculturation strategies, and basic dimensions of personality as they pertain to psychological adjustment among Hispanic students. Although personality characteristics have been shown to be important determinants of psychological well-being, acculturation research has put less emphasis on the role of personality in the well-being of immigrants. Hierarchical regression analysis showed that basic dimensions of personality such as extraversion and neuroticism were strongly related to psychological adjustment. Acculturation strategies did not mediate the effect of personality variables, but cultural resistance made a small, independent contribution to the explanation of some aspects of negative psychological adjustment. The implications of the results were discussed.

Estimating the Direct Radiative Effect of Absorbing Aerosols Overlying Marine Boundary Layer Clouds in the Southeast Atlantic Using MODIS and CALIOP

NASA Technical Reports Server (NTRS)

Meyer, Kerry; Platnick, Steven; Oreopoulos, Lazaros; Lee, Dongmin

2013-01-01

Absorbing aerosols such as smoke strongly absorb solar radiation, particularly at ultraviolet and visible/near-infrared (VIS/NIR) wavelengths, and their presence above clouds can have considerable implications. It has been previously shown that they have a positive (i.e., warming) direct aerosol radiative effect (DARE) when overlying bright clouds. Additionally, they can cause biased passive instrument satellite retrievals in techniques that rely on VIS/NIR wavelengths for inferring the cloud optical thickness (COT) and effective radius (re) of underlying clouds, which can in turn yield biased above-cloud DARE estimates. Here we investigate Moderate Resolution Imaging Spectroradiometer (MODIS) cloud optical property retrieval biases due to overlying absorbing aerosols observed by Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and examine the impact of these biases on above-cloud DARE estimates. The investigation focuses on a region in the southeast Atlantic Ocean during August and September (2006-2011), where smoke from biomass burning in southern Africa overlies persistent marine boundary layer stratocumulus clouds. Adjusting for above-cloud aerosol attenuation yields increases in the regional mean liquid COT (averaged over all ocean-only liquid clouds) by roughly 6%; mean re increases by roughly 2.6%, almost exclusively due to the COT adjustment in the non-orthogonal retrieval space. It is found that these two biases lead to an underestimate of DARE. For liquid cloud Aqua MODIS pixels with CALIOP-observed above-cloud smoke, the regional mean above-cloud radiative forcing efficiency (DARE per unit aerosol optical depth (AOD)) at time of observation (near local noon for Aqua overpass) increases from 50.9Wm(sup-2)AOD(sup-1) to 65.1Wm(sup-2)AOD(sup -1) when using bias-adjusted instead of nonadjusted MODIS cloud retrievals.

Cross-Sectional HIV Incidence Estimation in HIV Prevention Research

PubMed Central

Brookmeyer, Ron; Laeyendecker, Oliver; Donnell, Deborah; Eshleman, Susan H.

2013-01-01

Accurate methods for estimating HIV incidence from cross-sectional samples would have great utility in prevention research. This report describes recent improvements in cross-sectional methods that significantly improve their accuracy. These improvements are based on the use of multiple biomarkers to identify recent HIV infections. These multi-assay algorithms (MAAs) use assays in a hierarchical approach for testing that minimizes the effort and cost of incidence estimation. These MAAs do not require mathematical adjustments for accurate estimation of the incidence rates in study populations in the year prior to sample collection. MAAs provide a practical, accurate, and cost-effective approach for cross-sectional HIV incidence estimation that can be used for HIV prevention research and global epidemic monitoring. PMID:23764641

Evoked Death-Related Thoughts in the Aftermath of Terror Attack: The Associations Between Mortality Salience Effect and Adjustment Disorder.

PubMed

Ring, Lia; Lavenda, Osnat; Hamama-Raz, Yaira; Ben-Ezra, Menachem; Pitcho-Prelorentzos, Shani; David, Udi Y; Zaken, Adi; Mahat-Shamir, Michal

2018-01-01

ICD-11 has provided a revised definition for adjustment disorder (AjD). The current study examined whether mortality salience effect, a possible consequence of a terror attack, may serve as a significant predictor associated with each of the AjD subscales. Using an online survey, 379 adult participants were recruited and filled out self-reported questionnaires dealing with adjustment disorder symptoms as well as mortality salience effect. Findings revealed that mortality salience effect was a significant predictor of all AjD subscales. The importance of mortality salience effect for AjD is discussed in light of terror management theory.

Estimating outcomes and cost effectiveness using a single-arm clinical trial: ofatumumab for double-refractory chronic lymphocytic leukemia.

PubMed

Hatswell, Anthony J; Thompson, Gwilym J; Maroudas, Penny A; Sofrygin, Oleg; Delea, Thomas E

2017-01-01

Ofatumumab (Arzerra ® , Novartis) is a treatment for chronic lymphocytic leukemia refractory to fludarabine and alemtuzumab [double refractory (DR-CLL)]. Ofatumumab was licensed on the basis of an uncontrolled Phase II study, Hx-CD20-406, in which patients receiving ofatumumab survived for a median of 13.9 months. However, the lack of an internal control arm presents an obstacle for the estimation of comparative effectiveness. The objective of the study was to present a method to estimate the cost effectiveness of ofatumumab in the treatment of DR-CLL. As no suitable historical control was available for modelling, the outcomes from non-responders to ofatumumab were used to model the effect of best supportive care (BSC). This was done via a Cox regression to control for differences in baseline characteristics between groups. This analysis was included in a partitioned survival model built in Microsoft ® Excel with utilities and costs taken from published sources, with costs and quality-adjusted life years (QALYs) were discounted at a rate of 3.5% per annum. Using the outcomes seen in non-responders, ofatumumab is expected to add approximately 0.62 life years (1.50 vs. 0.88). Using published utility values this translates to an additional 0.30 QALYs (0.77 vs. 0.47). At the list price, ofatumumab had a cost per QALY of £130,563, and a cost per life year of £63,542. The model was sensitive to changes in assumptions regarding overall survival estimates and utility values. This study demonstrates the potential of using data for non-responders to model outcomes for BSC in cost-effectiveness evaluations based on single-arm trials. Further research is needed on the estimation of comparative effectiveness using uncontrolled clinical studies.

The Effects of Marital Conflict on Korean Children's Appraisal of Conflict and Psychological Adjustment

ERIC Educational Resources Information Center

Oh, Kyung Ja; Lee, Soojin; Park, Soo Hyun

2011-01-01

This study examined the effects of marital conflict on Korean children's psychological adjustment and appraisal of hypothetical marital conflict situations. Children between the ages of 10 and 12 were divided into "high-conflict" (n = 58) and "low-conflict" (n = 58) groups based on their self-reported degree of perceived…

Parent emotion socialization and pre-adolescent's social and emotional adjustment: Moderating effects of autonomic nervous system reactivity.

PubMed

McQuade, Julia D; Breaux, Rosanna P

2017-12-01

This study examined whether measures of children's autonomic nervous system (ANS) reactivity to social stress moderated the effect of parent emotion socialization on children's social and emotional adjustment. Sixty-one children (9-13 years) completed a peer rejection task while their respiratory sinus arrhythmia reactivity (RSA-R) and skin conductance level reactivity (SCL-R) were assessed. Parents' report of supportive and non-supportive reactions to their child's negative emotions served as measures of emotion socialization. Measures of children's social and emotional adjustment included: teacher-rated peer rejection, aggression, and prosocial behavior and parent-rated aggressive/dysregulated behavior and emotion regulation skills. Measures of children's ANS reactivity moderated the effect of parent emotion socialization on children's adjustment. Supportive responses were more protective for children evidencing RSA augmentation whereas non-supportive responses were more detrimental for children evidencing low SCL-R. Thus children's ANS reactivity during social stress may represent a biological vulnerability that influences sensitivity to parent emotion socialization. Copyright © 2017 Elsevier B.V. All rights reserved.

Calculating summary statistics for population chemical biomonitoring in women of childbearing age with adjustment for age-specific natality.

PubMed

Axelrad, Daniel A; Cohen, Jonathan

2011-01-01

The effects of chemical exposures during pregnancy on children's health have been an increasing focus of environmental health research in recent years, leading to greater interest in biomonitoring of chemicals in women of childbearing age in the general population. Measurements of mercury in blood from the National Health and Nutrition Examination Survey are frequently reported for "women of childbearing age," defined to be of ages 16-49 years. The intent is to represent prenatal chemical exposure, but blood mercury levels increase with age. Furthermore, women of different ages have different probabilities of giving birth. We evaluated options to address potential bias in biomonitoring summary statistics for women of childbearing age by accounting for age-specific probabilities of giving birth. We calculated median and 95th percentile levels of mercury, PCBs, and cotinine using these approaches: option 1: women aged 16-49 years without natality adjustment; option 2: women aged 16-39 years without natality adjustment; option 3: women aged 16-49 years, adjusted for natality by age; option 4: women aged 16-49 years, adjusted for natality by age and race/ethnicity. Among the three chemicals examined, the choice of option has the greatest impact on estimated levels of serum PCBs, which are strongly associated with age. Serum cotinine levels among Black non-Hispanic women of childbearing age are understated when age-specific natality is not considered. For characterizing in utero exposures, adjustment using age-specific natality provides a substantial improvement in estimation of biomonitoring summary statistics. Copyright © 2010 Elsevier Inc. All rights reserved.

[Effect of 2 methods of occlusion adjustment on occlusal balance and muscles of mastication in patient with implant restoration].

PubMed

Wang, Rong; Xu, Xin

2015-12-01

To compare the effect of 2 methods of occlusion adjustment on occlusal balance and muscles of mastication in patients with dental implant restoration. Twenty patients, each with a single edentulous posterior dentition with no distal dentition were selected, and divided into 2 groups. Patients in group A underwent original occlusion adjustment method and patients in group B underwent occlusal plane reduction technique. Ankylos implants were implanted in the edentulous space in each patient and restored with fixed prosthodontics single unit crown. Occlusion was adjusted in each restoration accordingly. Electromyograms were conducted to determine the effect of adjustment methods on occlusion and muscles of mastication 3 months and 6 months after initial restoration and adjustment. Data was collected and measurements for balanced occlusal measuring standards were obtained, including central occlusion force (COF), asymmetry index of molar occlusal force(AMOF). Balanced muscles of mastication measuring standards were also obtained including measurements from electromyogram for the muscles of mastication and the anterior bundle of the temporalis muscle at the mandibular rest position, average electromyogram measurements of the anterior bundle of the temporalis muscle at the intercuspal position(ICP), Astot, masseter muscle asymmetry index, and anterior temporalis asymmetry index (ASTA). Statistical analysis was performed using Student 's t test with SPSS 18.0 software package. Three months after occlusion adjustment, parameters of the original occlusion adjustment method were significantly different between group A and group B in balanced occlusal measuring standards and balanced muscles of mastication measuring standards. Six months after occlusion adjustment, parameters of the original occlusion adjustment methods were significantly different between group A and group B in balanced muscles of mastication measuring standards, but was no significant difference in balanced

Mechanism For Adjustment Of Commutation Of Brushless Motor

NASA Technical Reports Server (NTRS)

Schaefer, Richard E.

1995-01-01

Mechanism enables adjustment of angular position of set of Hall-effect devices that sense instantaneous shaft angle of brushless dc motor. Outputs of sensors fed to commutation circuitry. Measurement of shaft angle essential for commutation; that is, application of voltage to stator windings must be synchronized with shaft angle. To obtain correct angle measurement for commutation, Hall-effect angle sensors positioned at proper reference angle. The present mechanism accelerates adjustment procedure and makes it possible to obtain more accurate indication of minimum-current position because it provides for adjustment while motor running.

Productivity growth in outpatient child and adolescent mental health services: the impact of case-mix adjustment.

PubMed

Halsteinli, Vidar; Kittelsen, Sverre A; Magnussen, Jon

2010-02-01

The performance of health service providers may be monitored by measuring productivity. However, the policy value of such measures may depend crucially on the accuracy of input and output measures. In particular, an important question is how to adjust adequately for case-mix in the production of health care. In this study, we assess productivity growth in Norwegian outpatient child and adolescent mental health service units (CAMHS) over a period characterized by governmental utilization of simple productivity indices, a substantial increase in capacity and a concurrent change in case-mix. We analyze the sensitivity of the productivity growth estimates using different specifications of output to adjust for case-mix differences. Case-mix adjustment is achieved by distributing patients into eight groups depending on reason for referral, age and gender, as well as correcting for the number of consultations. We utilize the nonparametric Data Envelopment Analysis (DEA) method to implicitly calculate weights that maximize each unit's efficiency. Malmquist indices of technical productivity growth are estimated and bootstrap procedures are performed to calculate confidence intervals and to test alternative specifications of outputs. The dataset consist of an unbalanced panel of 48-60 CAMHS in the period 1998-2006. The mean productivity growth estimate from a simple unadjusted patient model (one single output) is 35%; adjusting for case-mix (eight outputs) reduces the growth estimate to 15%. Adding consultations increases the estimate to 28%. The latter reflects an increase in number of consultations per patient. We find that the governmental productivity indices strongly tend to overestimate productivity growth. Case-mix adjustment is of major importance and governmental utilization of performance indicators necessitates careful considerations of output specifications. Copyright 2009 Elsevier Ltd. All rights reserved.

47 CFR 54.509 - Adjustments to the discount matrix.

Code of Federal Regulations, 2011 CFR

2011-10-01

... (CONTINUED) UNIVERSAL SERVICE Universal Service Support for Schools and Libraries § 54.509 Adjustments to the... amounts of funding for a funding year, schools, libraries, library consortia, and consortia including such... times other than within a filing period described in § 54.507(c), if the estimates schools and libraries...

47 CFR 54.509 - Adjustments to the discount matrix.

Code of Federal Regulations, 2012 CFR

2012-10-01

... (CONTINUED) UNIVERSAL SERVICE Universal Service Support for Schools and Libraries § 54.509 Adjustments to the... amounts of funding for a funding year, schools, libraries, library consortia, and consortia including such... times other than within a filing period described in § 54.507(c), if the estimates schools and libraries...

47 CFR 54.509 - Adjustments to the discount matrix.

Code of Federal Regulations, 2010 CFR

2010-10-01

... amounts of funding for a funding year, schools, libraries, library consortia, and consortia including such... (CONTINUED) UNIVERSAL SERVICE Universal Service Support for Schools and Libraries § 54.509 Adjustments to the... times other than within a filing period described in § 54.507(c), if the estimates schools and libraries...

Effectiveness of inactivated influenza vaccines in preventing influenza-associated deaths and hospitalizations among Ontario residents aged ≥ 65 years: estimates with generalized linear models accounting for healthy vaccinee effects.

PubMed

Ridenhour, Benjamin J; Campitelli, Michael A; Kwong, Jeffrey C; Rosella, Laura C; Armstrong, Ben G; Mangtani, Punam; Calzavara, Andrew J; Shay, David K

2013-01-01

Estimates of the effectiveness of influenza vaccines in older adults may be biased because of difficulties identifying and adjusting for confounders of the vaccine-outcome association. We estimated vaccine effectiveness for prevention of serious influenza complications among older persons by using methods to account for underlying differences in risk for these complications. We conducted a retrospective cohort study among Ontario residents aged ≥ 65 years from September 1993 through September 2008. We linked weekly vaccination, hospitalization, and death records for 1.4 million community-dwelling persons aged ≥ 65 years. Vaccine effectiveness was estimated by comparing ratios of outcome rates during weeks of high versus low influenza activity (defined by viral surveillance data) among vaccinated and unvaccinated subjects by using log-linear regression models that accounted for temperature and time trends with natural spline functions. Effectiveness was estimated for three influenza-associated outcomes: all-cause deaths, deaths occurring within 30 days of pneumonia/influenza hospitalizations, and pneumonia/influenza hospitalizations. During weeks when 5% of respiratory specimens tested positive for influenza A, vaccine effectiveness among persons aged ≥ 65 years was 22% (95% confidence interval [CI], -6%-42%) for all influenza-associated deaths, 25% (95% CI, 13%-37%) for deaths occurring within 30 days after an influenza-associated pneumonia/influenza hospitalization, and 19% (95% CI, 4%-31%) for influenza-associated pneumonia/influenza hospitalizations. Because small proportions of deaths, deaths after pneumonia/influenza hospitalizations, and pneumonia/influenza hospitalizations were associated with influenza virus circulation, we estimated that vaccination prevented 1.6%, 4.8%, and 4.1% of these outcomes, respectively. By using confounding-reducing techniques with 15 years of provincial-level data including vaccination and health outcomes, we estimated that

A comparison of estimated and calculated effective porosity

NASA Astrophysics Data System (ADS)

Stephens, Daniel B.; Hsu, Kuo-Chin; Prieksat, Mark A.; Ankeny, Mark D.; Blandford, Neil; Roth, Tracy L.; Kelsey, James A.; Whitworth, Julia R.

Effective porosity in solute-transport analyses is usually estimated rather than calculated from tracer tests in the field or laboratory. Calculated values of effective porosity in the laboratory on three different textured samples were compared to estimates derived from particle-size distributions and soil-water characteristic curves. The agreement was poor and it seems that no clear relationships exist between effective porosity calculated from laboratory tracer tests and effective porosity estimated from particle-size distributions and soil-water characteristic curves. A field tracer test in a sand-and-gravel aquifer produced a calculated effective porosity of approximately 0.17. By comparison, estimates of effective porosity from textural data, moisture retention, and published values were approximately 50-90% greater than the field calibrated value. Thus, estimation of effective porosity for chemical transport is highly dependent on the chosen transport model and is best obtained by laboratory or field tracer tests. Résumé La porosité effective dans les analyses de transport de soluté est habituellement estimée, plutôt que calculée à partir d'expériences de traçage sur le terrain ou au laboratoire. Les valeurs calculées de la porosité effective au laboratoire sur trois échantillons de textures différentes ont été comparées aux estimations provenant de distributions de taille de particules et de courbes caractéristiques sol-eau. La concordance était plutôt faible et il semble qu'il n'existe aucune relation claire entre la porosité effective calculée à partir des expériences de traçage au laboratoire et la porosité effective estimée à partir des distributions de taille de particules et de courbes caractéristiques sol-eau. Une expérience de traçage de terrain dans un aquifère de sables et de graviers a fourni une porosité effective calculée d'environ 0,17. En comparaison, les estimations de porosité effective de données de

Academic self-concept in high school: predictors and effects on adjustment in higher education.

PubMed

Wouters, Sofie; Germeijs, Veerle; Colpin, Hilde; Verschueren, Karine

2011-12-01

Academic self-concept is considered a relevant psychological construct influencing many educational outcomes directly or indirectly. Therefore, the major focus of the current study is on the predictors and effects of academic self-concept in late adolescence. First, we studied the simultaneous effects of individual, class-average and school-average achievement (i.e., assessed by school grades) on academic self-concept in the final year of high school, thereby replicating and extending previous research on the big-fish-little-pond effect model. Second, the predictive value of high school academic self-concept for academic adjustment and success in the first year of higher education was examined. The sample comprised 536 twelfth grade students (44% boys) recruited from 24 schools (67 classes) that were representative with regard to geographical region and educational network in Flanders. Structural equation modeling showed that, when examining the joint contribution of school- and class-average achievement, only class-average achievement was significantly and negatively associated with academic self-concept. Furthermore, a significant effect of academic self-concept in high school on academic adjustment and success in higher education (in addition to any effects of high school academic achievement) was found. These results highlight the importance of considering academic self-concept in educational research and policy. © 2011 The Authors. Scandinavian Journal of Psychology © 2011 The Scandinavian Psychological Associations.

75 FR 4592 - January 2010 Pay Adjustments

Federal Register 2010, 2011, 2012, 2013, 2014

2010-01-28

... OFFICE OF PERSONNEL MANAGEMENT January 2010 Pay Adjustments AGENCY: U.S. Office of Personnel Management. ACTION: Notice. SUMMARY: The President adjusted the rates of basic pay and locality payments for certain categories of Federal employees effective in January 2010. This notice documents those pay...

Instrumental variables estimates of peer effects in social networks.

PubMed

An, Weihua

2015-03-01

Estimating peer effects with observational data is very difficult because of contextual confounding, peer selection, simultaneity bias, and measurement error, etc. In this paper, I show that instrumental variables (IVs) can help to address these problems in order to provide causal estimates of peer effects. Based on data collected from over 4000 students in six middle schools in China, I use the IV methods to estimate peer effects on smoking. My design-based IV approach differs from previous ones in that it helps to construct potentially strong IVs and to directly test possible violation of exogeneity of the IVs. I show that measurement error in smoking can lead to both under- and imprecise estimations of peer effects. Based on a refined measure of smoking, I find consistent evidence for peer effects on smoking. If a student's best friend smoked within the past 30 days, the student was about one fifth (as indicated by the OLS estimate) or 40 percentage points (as indicated by the IV estimate) more likely to smoke in the same time period. The findings are robust to a variety of robustness checks. I also show that sharing cigarettes may be a mechanism for peer effects on smoking. A 10% increase in the number of cigarettes smoked by a student's best friend is associated with about 4% increase in the number of cigarettes smoked by the student in the same time period. Copyright © 2014 Elsevier Inc. All rights reserved.

Dynamic gauge adjustment of high-resolution X-band radar data for convective rain storms: Model-based evaluation against measured combined sewer overflow

NASA Astrophysics Data System (ADS)

Borup, Morten; Grum, Morten; Linde, Jens Jørgen; Mikkelsen, Peter Steen

2016-08-01

Numerous studies have shown that radar rainfall estimates need to be adjusted against rain gauge measurements in order to be useful for hydrological modelling. In the current study we investigate if adjustment can improve radar rainfall estimates to the point where they can be used for modelling overflows from urban drainage systems, and we furthermore investigate the importance of the aggregation period of the adjustment scheme. This is done by continuously adjusting X-band radar data based on the previous 5-30 min of rain data recorded by multiple rain gauges and propagating the rainfall estimates through a hydraulic urban drainage model. The model is built entirely from physical data, without any calibration, to avoid bias towards any specific type of rainfall estimate. The performance is assessed by comparing measured and modelled water levels at a weir downstream of a highly impermeable, well defined, 64 ha urban catchment, for nine overflow generating rain events. The dynamically adjusted radar data perform best when the aggregation period is as small as 10-20 min, in which case it performs much better than static adjusted radar data and data from rain gauges situated 2-3 km away.

Estimation of the Continuous and Discontinuous Leverage Effects

PubMed Central

Aït-Sahalia, Yacine; Fan, Jianqing; Laeven, Roger J. A.; Wang, Christina Dan; Yang, Xiye

2017-01-01

This paper examines the leverage effect, or the generally negative covariation between asset returns and their changes in volatility, under a general setup that allows the log-price and volatility processes to be Itô semimartingales. We decompose the leverage effect into continuous and discontinuous parts and develop statistical methods to estimate them. We establish the asymptotic properties of these estimators. We also extend our methods and results (for the continuous leverage) to the situation where there is market microstructure noise in the observed returns. We show in Monte Carlo simulations that our estimators have good finite sample performance. When applying our methods to real data, our empirical results provide convincing evidence of the presence of the two leverage effects, especially the discontinuous one. PMID:29606780

Estimation of the Continuous and Discontinuous Leverage Effects.

PubMed

Aït-Sahalia, Yacine; Fan, Jianqing; Laeven, Roger J A; Wang, Christina Dan; Yang, Xiye

2017-01-01

This paper examines the leverage effect, or the generally negative covariation between asset returns and their changes in volatility, under a general setup that allows the log-price and volatility processes to be Itô semimartingales. We decompose the leverage effect into continuous and discontinuous parts and develop statistical methods to estimate them. We establish the asymptotic properties of these estimators. We also extend our methods and results (for the continuous leverage) to the situation where there is market microstructure noise in the observed returns. We show in Monte Carlo simulations that our estimators have good finite sample performance. When applying our methods to real data, our empirical results provide convincing evidence of the presence of the two leverage effects, especially the discontinuous one.

Kinematic synthesis of adjustable robotic mechanisms

NASA Astrophysics Data System (ADS)

Chuenchom, Thatchai

1993-01-01

Conventional hard automation, such as a linkage-based or a cam-driven system, provides high speed capability and repeatability but not the flexibility required in many industrial applications. The conventional mechanisms, that are typically single-degree-of-freedom systems, are being increasingly replaced by multi-degree-of-freedom multi-actuators driven by logic controllers. Although this new trend in sophistication provides greatly enhanced flexibility, there are many instances where the flexibility needs are exaggerated and the associated complexity is unnecessary. Traditional mechanism-based hard automation, on the other hand, neither can fulfill multi-task requirements nor are cost-effective mainly due to lack of methods and tools to design-in flexibility. This dissertation attempts to bridge this technological gap by developing Adjustable Robotic Mechanisms (ARM's) or 'programmable mechanisms' as a middle ground between high speed hard automation and expensive serial jointed-arm robots. This research introduces the concept of adjustable robotic mechanisms towards cost-effective manufacturing automation. A generalized analytical synthesis technique has been developed to support the computational design of ARM's that lays the theoretical foundation for synthesis of adjustable mechanisms. The synthesis method developed in this dissertation, called generalized adjustable dyad and triad synthesis, advances the well-known Burmester theory in kinematics to a new level. While this method provides planar solutions, a novel patented scheme is utilized for converting prescribed three-dimensional motion specifications into sets of planar projections. This provides an analytical and a computational tool for designing adjustable mechanisms that satisfy multiple sets of three-dimensional motion specifications. Several design issues were addressed, including adjustable parameter identification, branching defect, and mechanical errors. An efficient mathematical scheme for

The economic burden of disease by industry: Differences in quality-adjusted life years and associated costs.

PubMed

Tolbert, Davina V; McCollister, Kathryn E; LeBlanc, William G; Lee, David J; Fleming, Lora E; Muennig, Peter

2014-07-01

This study compares differences in quality-adjusted life expectancy across the eight original National Occupational Research Agenda (NORA) industry sectors. Data from the 1997 to 2012 National Health Interview Survey (NHIS) were used to estimate quality-adjusted life years (QALYs) for all workers and by NORA sector. Differences in QALYs were calculated and translated into economic values using estimates of the societal willingness-to-pay per QALY. Mean QALYs across workers was 29.17 years. Among NORA sectors, wholesale, and retail trade workers had the highest average QALYs remaining (35.88), while mining workers had the lowest QALYs (31.4). The economic value of this difference ranges from $604,843 to $1,155,287 per worker depending on the societal willingness-to-pay per QALY. The value of life lost within some industries is very high relative to others. Additional investments in occupational safety, benefits, and health promotion initiatives may reduce these losses, but experimental research is needed to assess the effectiveness of such programs. © 2014 Wiley Periodicals, Inc.

Effects of a Brief Psychoeducational Intervention for Family Conflict: Constructive Conflict, Emotional Insecurity and Child Adjustment.

PubMed

Miller-Graff, Laura E; Cummings, E Mark; Bergman, Kathleen N

2016-10-01

The role of emotional security in promoting positive adjustment following exposure to marital conflict has been identified in a large number of empirical investigations, yet to date, no interventions have explicitly addressed the processes that predict child adjustment after marital conflict. The current study evaluated a randomized controlled trial of a family intervention program aimed at promoting constructive marital conflict behaviors thereby increasing adolescent emotional security and adjustment. Families (n = 225) were randomized into 1 of 4 conditions: Parent-Adolescent (n = 75), Parent-Only (n = 75), Self-Study (n = 38) and No Treatment (n = 37). Multi-informant and multi-method assessments were conducted at baseline, post-treatment and 6-month follow-up. Effects of treatment on destructive and constructive conflict behaviors were evaluated using multilevel models where observations were nested within individuals over time. Process models assessing the impact of constructive and destructive conflict behaviors on emotional insecurity and adolescent adjustment were evaluated using path modeling. Results indicated that the treatment was effective in increasing constructive conflict behaviors (d = 0.89) and decreasing destructive conflict behaviors (d = -0.30). For the Parent-Only Group, post-test constructive conflict behaviors directly predicted lower levels of adolescent externalizing behaviors at 6-month follow-up. Post-test constructive conflict skills also indirectly affected adolescent internalizing behaviors through adolescent emotional security. These findings support the use of a brief psychoeducational intervention in improving post-treatment conflict and emotional security about interparental relationships.

Regional ice-mass changes and glacial-isostatic adjustment in Antarctica from GRACE

NASA Astrophysics Data System (ADS)

Sasgen, Ingo; Martinec, Zdeněk; Fleming, Kevin

2007-12-01

We infer regional mass changes in Antarctica using ca. 4 years of Gravity Recovery and Climate Experiment (GRACE) level 2 data. We decompose the time series of the Stokes coefficients into their linear as well as annual and semi-annual components by a least-squares adjustment and apply a statistical reliability test to the Stokes potential-coefficients' linear temporal trends. Mass changes in three regions of Antarctica that display prominent geoid-height change are determined by adjusting predictions of glacier melting at the tip of the Antarctic Peninsula and in the Amundsen Sea Sector, and of the glacial-isostatic adjustment (GIA) over the Ronne Ice Shelf. We use the GFZ RL04, CNES RL01C, JPL RL04 and CSR RL04 potential-coefficient releases, and show that, although all data sets consistently reflect the prominent mass changes, differences in the mass-change estimates are considerably larger than the uncertainties estimated by the propagation of the GRACE errors. We then use the bootstrapping method based on the four releases and six time intervals, each with 3.5 years of data, to quantify the variability of the mean mass-change estimates. We find 95% of our estimates to lie within 0.08 and 0.09 mm/a equivalent sea-level (ESL) change for the Antarctic Peninsula and within 0.18 and 0.20 mm/a ESL for the Amundsen Sea Sector. Forward modelling of the GIA over the Ronne Ice Shelf region suggests that the Antarctic continent was covered by 8.4 to 9.4 m ESL of additional ice during the Last-Glacial Maximum (ca. 22 to 15 ka BP). With regards to the mantle-viscosity values and the glacial history used, this value is considered as a minimum estimate. The mass-change estimates derived from all GRACE releases and time intervals lie within ca. 20% (Amundsen Sea Sector), 30% (Antarctic Peninsula) and 50% (Ronne Ice Shelf region) of the bootstrap-estimated mean, demonstrating the reliability of results obtained using GRACE observations.

Estimating increases in outpatient dialysis costs resulting from scientific and technological advancement.

PubMed

Ozminkowski, R J; Hassol, A; Firkusny, I; Noether, M; Miles, M A; Newmann, J; Sharda, C; Guterman, S; Schmitz, R

1995-04-01

The Medicare program's base payment rate for outpatient dialysis services has never been adjusted for the effects of inflation, productivity changes, or scientific and technological advancement on the costs of treating patients with end-stage renal disease. In recognition of this, Congress asked the Prospective Payment Assessment Commission to annually recommend an adjustment to Medicare's base payment rate to dialysis facilities. One component of this adjustment addresses the cost-increasing effects of technological change--the scientific and technological advances (S&TA) component. The S&TA component is intended to encourage dialysis facilities to adopt technologies that, when applied appropriately, enhance the quality of patient care, even though they may also increase costs. We found the appropriate increase to the composite payment rate for Medicare outpatient dialysis services in fiscal year 1995 to vary from 0.18% to 2.18%. These estimates depend on whether one accounts for the lack of previous adjustments to the composite rate. Mathematically, the S&TA adjustment also depends on whether one considers the likelihood of missing some dialysis sessions because of illness or hospitalization. The S&TA estimates also allow for differences in the incremental costs of technological change that are based on the varying advice of experts in the dialysis industry. The major contributors to the cost of technological change in dialysis services are the use of twin-bag disconnect peritoneal dialysis systems, automated peritoneal dialysis cyclers, and the new generation of hemodialysis machines currently on the market. Factors beyond the control of dialysis facility personnel that influence the cost of patient care should be considered when payment rates are set, and those rates should be updated as market conditions change. The S&TA adjustment is one example of how the composite rate payment system for outpatient dialysis services can be modified to provide appropriate

Estimation and modeling of electrofishing capture efficiency for fishes in wadeable warmwater streams

USGS Publications Warehouse

Price, A.; Peterson, James T.

2010-01-01

Stream fish managers often use fish sample data to inform management decisions affecting fish populations. Fish sample data, however, can be biased by the same factors affecting fish populations. To minimize the effect of sample biases on decision making, biologists need information on the effectiveness of fish sampling methods. We evaluated single-pass backpack electrofishing and seining combined with electrofishing by following a dual-gear, mark–recapture approach in 61 blocknetted sample units within first- to third-order streams. We also estimated fish movement out of unblocked units during sampling. Capture efficiency and fish abundances were modeled for 50 fish species by use of conditional multinomial capture–recapture models. The best-approximating models indicated that capture efficiencies were generally low and differed among species groups based on family or genus. Efficiencies of single-pass electrofishing and seining combined with electrofishing were greatest for Catostomidae and lowest for Ictaluridae. Fish body length and stream habitat characteristics (mean cross-sectional area, wood density, mean current velocity, and turbidity) also were related to capture efficiency of both methods, but the effects differed among species groups. We estimated that, on average, 23% of fish left the unblocked sample units, but net movement varied among species. Our results suggest that (1) common warmwater stream fish sampling methods have low capture efficiency and (2) failure to adjust for incomplete capture may bias estimates of fish abundance. We suggest that managers minimize bias from incomplete capture by adjusting data for site- and species-specific capture efficiency and by choosing sampling gear that provide estimates with minimal bias and variance. Furthermore, if block nets are not used, we recommend that managers adjust the data based on unconditional capture efficiency.

Negative control exposure studies in the presence of measurement error: implications for attempted effect estimate calibration

PubMed Central

Sanderson, Eleanor; Macdonald-Wallis, Corrie; Davey Smith, George

2018-01-01

Abstract Background Negative control exposure studies are increasingly being used in epidemiological studies to strengthen causal inference regarding an exposure-outcome association when unobserved confounding is thought to be present. Negative control exposure studies contrast the magnitude of association of the negative control, which has no causal effect on the outcome but is associated with the unmeasured confounders in the same way as the exposure, with the magnitude of the association of the exposure with the outcome. A markedly larger effect of the exposure on the outcome than the negative control on the outcome strengthens inference that the exposure has a causal effect on the outcome. Methods We investigate the effect of measurement error in the exposure and negative control variables on the results obtained from a negative control exposure study. We do this in models with continuous and binary exposure and negative control variables using analysis of the bias of the estimated coefficients and Monte Carlo simulations. Results Our results show that measurement error in either the exposure or negative control variables can bias the estimated results from the negative control exposure study. Conclusions Measurement error is common in the variables used in epidemiological studies; these results show that negative control exposure studies cannot be used to precisely determine the size of the effect of the exposure variable, or adequately adjust for unobserved confounding; however, they can be used as part of a body of evidence to aid inference as to whether a causal effect of the exposure on the outcome is present. PMID:29088358

Negative control exposure studies in the presence of measurement error: implications for attempted effect estimate calibration.

PubMed

Sanderson, Eleanor; Macdonald-Wallis, Corrie; Davey Smith, George

2018-04-01

Negative control exposure studies are increasingly being used in epidemiological studies to strengthen causal inference regarding an exposure-outcome association when unobserved confounding is thought to be present. Negative control exposure studies contrast the magnitude of association of the negative control, which has no causal effect on the outcome but is associated with the unmeasured confounders in the same way as the exposure, with the magnitude of the association of the exposure with the outcome. A markedly larger effect of the exposure on the outcome than the negative control on the outcome strengthens inference that the exposure has a causal effect on the outcome. We investigate the effect of measurement error in the exposure and negative control variables on the results obtained from a negative control exposure study. We do this in models with continuous and binary exposure and negative control variables using analysis of the bias of the estimated coefficients and Monte Carlo simulations. Our results show that measurement error in either the exposure or negative control variables can bias the estimated results from the negative control exposure study. Measurement error is common in the variables used in epidemiological studies; these results show that negative control exposure studies cannot be used to precisely determine the size of the effect of the exposure variable, or adequately adjust for unobserved confounding; however, they can be used as part of a body of evidence to aid inference as to whether a causal effect of the exposure on the outcome is present.

Estimating a Change from TRICARE to Commercial Insurance Plans.

PubMed

Murray, Carla T; Schmit, Matthew

2018-03-14

We estimate the effect on health care spending of an option to change TRICARE. Under the option, which is based on a proposal made by the Military Compensation and Retirement Modernization Commission (MCRMC), most beneficiaries could choose from a range of commercial health networks instead of the current TRICARE plans. Military treatment facilities would become network providers under the commercial plans. We used data from the Department of Defense (DoD) to estimate the cost of providing the current health care benefit to working-age retirees and their dependents and survivors, and active duty family members. We then adjusted those data to estimate what the private insurance premiums would be for those groups. Greater details about the methodology can be found in earlier work by the Congressional Budget Office. Because payments by TRICARE to physicians and hospitals are tied to payments made by Medicare, we used the information from studies that compare Medicare payment rates to rates paid to doctors and hospitals by private insurance to estimate what it would cost private insurers to provide approximately the same level of care, with adjustments to account for the higher out-of-pocket costs that beneficiaries would pay under the option. We also made adjustments to account for the possibility that many beneficiaries would decrease their use of the MTFs in favor of private providers, which could increase the overall costs of DoD. We then estimated that increasing the cost sharing to a level found in popular civilian plans would lower overall demand for services by about 10% for military retiree households and about 18% for active duty family members. We estimated that DoD would pay subsidies to retain about half of the excess capacity created by beneficiaries switching their care from MTFs to the private sector. Evaluated at the midpoint of the ranges, the net effect on DoD's budget would be approximately $0, we estimate, but costs could fall in a likely range

Child adjustment in high conflict families.

PubMed

Smith, J; Berthelsen, D; O'Connor, I

1997-03-01

Children exposed to spousal violence are at risk for social-emotional problems. This research investigated a number of family and child factors which might influence the effects of witnessing spousal violence on young children. Fifty-four mothers who had at least one child in the age range of 3 to 6 years participated in the study. These women had left a violent relationship 12 to 24 months prior to their participation in the study and were not in a new relationship. Information was collected through a structured interview which included the administration of a standardized family violence measure (conflict tactics scale) and child adjustment profile (child behaviour checklist). Forty-two per cent of the children exhibited a level of behavioural problems which would warrant clinical intervention. The amount of violence that the children witnessed, the children's responses when the violence occurred and whether the child copied the violent partner's behaviour, were associated with the children's behavioural adjustment scores. Maternal parenting style was not found to have a significant effect on behavioural adjustment. The study provided important quantitative and qualitative data on the nature of parent-child relationships and children's adjustment in families where there is spousal violence.

Nonparametric estimation and testing of fixed effects panel data models

PubMed Central

Henderson, Daniel J.; Carroll, Raymond J.; Li, Qi

2009-01-01

In this paper we consider the problem of estimating nonparametric panel data models with fixed effects. We introduce an iterative nonparametric kernel estimator. We also extend the estimation method to the case of a semiparametric partially linear fixed effects model. To determine whether a parametric, semiparametric or nonparametric model is appropriate, we propose test statistics to test between the three alternatives in practice. We further propose a test statistic for testing the null hypothesis of random effects against fixed effects in a nonparametric panel data regression model. Simulations are used to examine the finite sample performance of the proposed estimators and the test statistics. PMID:19444335

Rank-based estimation in the {ell}1-regularized partly linear model for censored outcomes with application to integrated analyses of clinical predictors and gene expression data.