Search results for "selection bias"
showing 10 items of 49 documents
The financial burden of non-communicable chronic diseases in rural Nigeria: Wealth and gender heterogeneity in health care utilization and health exp…
2016
Objectives Better insights into health care utilization and out-of-pocket expenditures for non-communicable chronic diseases (NCCD) are needed to develop accessible health care and limit the increasing financial burden of NCCDs in Sub-Saharan Africa. Methods A household survey was conducted in rural Kwara State, Nigeria, among 5,761 individuals. Data were obtained using biomedical and socio-economic questionnaires. Health care utilization, NCCD-related health expenditures and distances to health care providers were compared by sex and by wealth quintile, and a Heckman regression model was used to estimate health expenditures taking selection bias in health care utilization into account. Res…
Comorbidity between obesity and attention deficit/hyperactivity disorder: Population study with 13–15-year-olds
2006
Objective: This study analyzes whether obese children have a higher risk of attention deficit/hyperactivity “characteristics” (AD/HD) than do children with other nutritional states. Method: This study included 35,403 participants from 486 community schools. They completed the AD/HD scale of the Strengths and Difficulties Questionnaire (SDQ) and were weighed and measured. 2879 of the participants were obese and 78 were morbidly obese (BMI >40). Results: A discrete, nonsignificant, increment was found in the AD/HD characteristics of male participants with morbid obesity, as compared with the other nutritional states. Among morbidly obese females, the prevalence of AD/HD characteristics was sl…
Lower self-reported depression in patients with erectile dysfunction after treatment with sildenafil
2001
Abstract Background: Depressive symptoms in men with erectile dysfunction (ED) may improve under successful ED treatment. Self-reported depressive symptoms were compared in men with ED after sildenafil treatment to a group of untreated patients. Methods: In an open study, self-reported depressive symptoms of 54 men after successful treatment with sildenafil (>4 weeks) and 51 men awaiting ED treatment were investigated with the Center of Epidemiologic Studies–Depression Scale (CES–D). CES–D items were subjected to an exploratory factor analysis and group differences in CES–D items and factors were analyzed. Results: Groups were comparable with respect to demographic characteristics and illne…
Investigating the association between cancer and the risk of dementia: Results from the Memento cohort
2021
International audience; IntroductionStudies on the association of cancer and risk of dementia are inconclusive due to result heterogeneity and concerns of survivor bias and unmeasured confounding.MethodsThis study uses data from the Memento cohort, a French multicenter cohort following persons with either mild or isolated cognitive complaints for a median of 5 years. Illness‐death models (IDMs) were used to estimate transition‐specific hazard ratios (HRs) and 95% confidence intervals (CIs) for incident cancer in relation to dementia from time since study entry.ResultsThe analytical sample (N = 2258) excluded 65 individuals without follow‐up information. At the end of follow‐up, 286 individu…
Selection bias during recruitment of elderly subjects from the general population for psychiatric interviews
1997
The aim of the present study was to determine and assess a possible selection bias in an epidemiologic investigation in the elderly. A stratified sample of 1305 probands aged 60-99 years was initially contacted by mail and then by telephone to obtain their consent to participate in a psychiatric interview. A liberal recruitment procedure led to interview participation of only 291 subjects. The proportion of younger, male, and married subjects participating in the study was greater than that of elderly, female, and single or widowed subjects. Subjects without a psychiatric lifetime diagnosis were more cooperative than those with a psychiatric disorder. The latter finding demonstrates the nee…
Respondent Uncertainty and Ordering Effect on Willingness to Pay for Salt Marsh Conservation in the Brest Roadstead (France)
2017
International audience; This paper explores the potential link between the sensitivity of willingness to pay (WTP) to the order of presenting bid amounts in contingent valuation questions (ordering effect) and respondent uncertainty. The resource being valued is a public project to protect salt marshes against the spread of an invasive aquatic plant in the Brest roadstead (France). Valuation uncertainty is captured through a variant of payment card format where respondents are given the opportunity to report their WTP as either a single value (Option A) or an interval of values (Option B). The ordering effect is tested using both parametric models that ignore and control for the potential s…
The categorization of amateur cyclists as research participants: findings from an observational study.
2018
Sampling bias is an issue for research involving cyclists. The heterogeneity of cyclist populations, on the basis of skill level and riding purpose, can generate incorrect inferences about one specific segment of the population of interest. In addition, a more accurate categorization would be helpful when physiological parameters are not available. This study proposes using self-reported data to categorize amateur cyclist types by varying skill levels and riding purposes, therefore improving sample selection in experimental studies. A total of 986 cyclists completed an online questionnaire between February and October 2016. Two-step cluster analyses were performed to generate distinct group…
Selection bias was reduced by recontacting nonparticipants
2016
Objective One of the main goals of health examination surveys is to provide unbiased estimates of health indicators at the population level. We demonstrate how multiple imputation methods may help to reduce the selection bias if partial data on some nonparticipants are collected. Study Design and Setting In the FINRISK 2007 study, a population-based health study conducted in Finland, a random sample of 10,000 men and women aged 25–74 years were invited to participate. The study included a questionnaire data collection and a health examination. A total of 6,255 individuals participated in the study. Out of 3,745 nonparticipants, 473 returned a simplified questionnaire after a recontact. Both…
Using active learning to adapt remote sensing image classifiers
2011
The validity of training samples collected in field campaigns is crucial for the success of land use classification models. However, such samples often suffer from a sample selection bias and do not represent the variability of spectra that can be encountered in the entire image. Therefore, to maximize classification performance, one must perform adaptation of the first model to the new data distribution. In this paper, we propose to perform adaptation by sampling new training examples in unknown areas of the image. Our goal is to select these pixels in an intelligent fashion that minimizes their number and maximizes their information content. Two strategies based on uncertainty and cluster…
On the value of drovers’ routes as environmental assets: A contingent valuation approach
2013
The aim of this study was to evaluate the non-market benefits resulting from the restoration of an old drovers’ route for recreation uses in Valencia (Spain). The valuation was carried out using the Contingent Valuation Method (CVM) through the elicitation of individuals’ willingness to pay (WTP). Since 52% of the respondents stated a zero WTP response, in order to inform decision-making processes more accurately, special attention was paid to the problem of zero and protest responses, and also to the possible presence of self-selection by those that protested. For the different specifications considered, results suggest that mean WTP estimates are higher for “rural areas” than for “the Val…