bluuebunny/crossref_metadata_2025_split huggingface dataset:
Small Confidence Sets for the Mean of a Spherically Symmetric Distribution
Authors: Samworth Richard 
Published: May 2005

SummarySuppose that X has a k-variate spherically symmetric distribution with mean vector θ and identity covariance matrix. We present two spherical confidence sets for θ, both centred at a positive part Stein estimator TS+(X). In the first, we obtain the radius by approximating the upper α-point of the sampling distribution of ‖TS+(X)−θ‖2 by the first two non-zero terms of its Taylor series about the origin. We can analyse some of the properties of this confidence set and see that it performs well in terms of coverage probability, volume and conditional behaviour. In the second method, we find the radius by using a parametric bootstrap procedure. Here, even greater improvement in terms of volume over the usual confidence set is possible, at the expense of having a less explicit radius function. A real data example is provided, and extensions to the unknown covariance matrix and elliptically symmetric cases are discussed.
Properties of Bagged Nearest Neighbour Classifiers
Authors: Hall Peter , Samworth Richard J. 
Published: May 2005

SummaryIt is shown that bagging, a computationally intensive method, asymptotically improves the performance of nearest neighbour classifiers provided that the resample size is less than 69% of the actual sample size, in the case of with-replacement bagging, or less than 50% of the sample size, for without-replacement bagging. However, for larger sampling fractions there is no asymptotic difference between the risk of the regular nearest neighbour classifier and its bagged version. In particular, neither achieves the large sample performance of the Bayes classifier. In contrast, when the sampling fractions converge to 0, but the resample sizes diverge to ∞, the bagged classifier converges to the optimal Bayes rule and its risk converges to the risk of the latter. These results are most readily seen when the two populations have well-defined densities, but they may also be derived in other cases, where densities exist in only a relative sense. Cross-validation can be used effectively to choose the sampling fraction. Numerical calculation is used to illustrate these theoretical properties.
Self-Weighted Least Absolute Deviation Estimation for Infinite Variance Autoregressive Models
Authors: Ling Shiqing 
Published: May 2005

SummaryHow to undertake statistical inference for infinite variance autoregressive models has been a long-standing open problem. To solve this problem, we propose a self-weighted least absolute deviation estimator and show that this estimator is asymptotically normal if the density of errors and its derivative are uniformly bounded. Furthermore, a Wald test statistic is developed for the linear restriction on the parameters, and it is shown to have non-trivial local power. Simulation experiments are carried out to assess the performance of the theory and method in finite samples and a real data example is given. The results are entirely different from other published results and should provide new insights for future research on heavy-tailed time series.
Statistical Inference for Discretely Observed Markov Jump Processes
Authors: Bladt Mogens , Sørensen Michael 
Published: May 2005

SummaryLikelihood inference for discretely observed Markov jump processes with finite state space is investigated. The existence and uniqueness of the maximum likelihood estimator of the intensity matrix are investigated. This topic is closely related to the imbedding problem for Markov chains. It is demonstrated that the maximum likelihood estimator can be found either by the EM algorithm or by a Markov chain Monte Carlo procedure. When the maximum likelihood estimator does not exist, an estimator can be obtained by using a penalized likelihood function or by the Markov chain Monte Carlo procedure with a suitable prior. The methodology and its implementation are illustrated by examples and simulation studies.
Variance of the Number of False Discoveries
Authors: Owen Art B. 
Published: May 2005

SummaryIn high throughput genomic work, a very large number d of hypotheses are tested based on n≪d data samples. The large number of tests necessitates an adjustment for false discoveries in which a true null hypothesis was rejected. The expected number of false discoveries is easy to obtain. Dependences between the hypothesis tests greatly affect the variance of the number of false discoveries. Assuming that the tests are independent gives an inadequate variance formula. The paper presents a variance formula that takes account of the correlations between test statistics. That formula involves O(d2) correlations, and so a naïve implementation has cost O(nd2). A method based on sampling pairs of tests allows the variance to be approximated at a cost that is independent of d.
Calibrated Imputation in Surveys Under a Quasi-Model-Assisted Approach
Authors: Beaumont Jean-François 
Published: May 2005

SummaryWe propose to use calibrated imputation to compensate for missing values. This technique consists of finding final imputed values that are as close as possible to preliminary imputed values and are calibrated to satisfy constraints. Preliminary imputed values, potentially justified by an imputation model, are obtained through deterministic single imputation. Using appropriate constraints, the resulting imputed estimator is asymptotically unbiased for estimation of linear population parameters such as domain totals. A quasi-model-assisted approach is considered in the sense that inferences do not depend on the validity of an imputation model and are made with respect to the sampling design and a non-response model. An imputation model may still be used to generate imputed values and thus to improve the efficiency of the imputed estimator. This approach has the characteristic of handling naturally the situation where more than one imputation method is used owing to missing values in the variables that are used to obtain imputed values. We use the Taylor linearization technique to obtain a variance estimator under a general non-response model. For the logistic non-response model, we show that ignoring the effect of estimating the non-response model parameters leads to overestimating the variance of the imputed estimator. In practice, the overestimation is expected to be moderate or even negligible, as shown in a simulation study.
The information needs and information‐seeking behaviours of home‐care workers and clients receiving home care
Authors: Cooper Janet , Urquhart Christine 
Published: May 2005

AbstractAims and objectives:  Discusses findings from doctoral research on the information behaviour of home‐care workers and their clients. The paper focuses on the findings, which have implications for health library and information services.Sample and methods:  The qualitative research methods included participant observation in the homes of clients (n = 7), over a period of 18 months, in a city in the UK, complemented by in‐depth interviews of home‐care staff (n = 47).Results:  Home‐care staff perceived requests for information on a variety of topics as an indivisible part of their caring role. Clients asked for more information than they had in the past, and home‐care workers were expected to respond to a wide variety of enquiries about health, welfare, leisure and domestic concerns. Clients trusted their advice as much as they might have trusted members of the family. Home‐care workers from an agency used a variety of resources at the agency office to help them, such as leaflets on welfare benefits, and health conditions. Few had used NHS Direct, and library use (by a third of the home‐care workers) was generally associated with course work or training. Some family members and home‐care staff used self‐help groups, but the research found that family members were sometimes reticent to ask advice on sensitive issues in self‐help groups. Home‐care workers learnt from each other and shared experience.Conclusions:  Libraries and information services need to target provision of formal information carefully, as it is advice and counsel that is required in the home‐care setting.
Chasing the Sun: a virtual reference service between SAHSLC (SA) and SWICE (UK)
Authors: Rockliff Sue , Peterson Mary , Martin Kath , Curtis Dorothy 
Published: May 2005

AbstractAim:  In 2002, a discussion in the United Kingdom (UK) between South‐west Information for Clinical Effectiveness (SWICE) librarians and a member of the South Australian Department of Human Services Libraries’ Consortium (SAHSLC) raised the possibility of developing an after‐hours virtual reference service between the two consortium groups. The aim of the service is to put medical practitioners in contact with a librarian when urgent help is required in finding clinical medical information after hours.Methods:  A trial project has begun and has been given the name ‘Chasing the Sun’. The service will make use of time‐zone differences between the UK and Australia, so that librarians at work in another country will be able to answer urgent patient‐related queries that cannot wait until normal office hours.Results:  This paper looks at the development of ‘Chasing the Sun’ from initial concept, funding proposal and trial project stage to implementation. It includes details of the groundwork, software evaluation, trials, outcomes, cost and benefits, future directions and potential problems yet to be experienced or overcome.Conclusion:  This service is the first of its kind between health libraries in the world and offers potential for future worldwide expansion.
Impacts of Managed Care Patient Protection Laws on Health Services Utilization and Patient Satisfaction with Care
Authors: Sloan Frank A. , Rattliff John R. , Hall Mark A. 
Published: May 2005

Objective. To assess effects of patient protection laws implemented by the vast majority of states during the 1990s on the public's satisfaction and trust relating to health care, and on key utilization measures.Data Sources/Study Setting. Measures of individuals' health care utilization and satisfaction, and control variables, came from three waves of the Community Tracking Study (CTS) Household Surveys conducted in 1996–1997, 1998–1999, and 2000–2001. The CTS was conducted in 60 randomly selected communities, throughout the U.S. In addition, a supplemental national sample of households from CTS was also included, resulting in a combined sample with cases from 48 states and the District of Columbia. After applying exclusion restrictions, the analysis sample was 149,688 adults.Study Design. Using a fixed‐effects methodology, we assessed the influence of patient protection laws on satisfaction with care and utilization of services for the entire sample and for subsamples of persons in poor health, with low income, and who were enrolled in HMOs.Data Collection/Extraction Methods. One of the authors (Hall) compiled relevant laws in all U.S. states through 2001 from primary legal sources, checking for accuracy by conducting independent research on statutory changes and by asking three to five regulators in each state to verify that the information was correct.Principal Findings. Overall, patient protection laws had little or no effect on either trust, satisfaction with care, or utilization. Significance was found postenactment of a state patient protection law only for emergency room visits in the general sample, and only for physician trust in the low‐income sample. Because of the number of possible associations examined, occasional findings of significance could occur by chance.Conclusions.Enactment of managed care patient protection laws did not generally increase utilization of health services or improve patient satisfaction with care.
The Effect of Medicaid Payment Generosity on Access and Use among Beneficiaries
Authors: Shen Yu‐Chu , Zuckerman Stephen 
Published: May 2005

Objective. This study examines the effects of Medicaid payment generosity on access and care for adult and child Medicaid beneficiaries.Data Source. Three years of the National Surveys of America's Families (1997, 1999, 2002) are linked to the Urban Institute Medicaid capitation rate surveys, the Area Resource File, and the American Hospital Association survey files.Study Design. In order to identify the effect of payment generosity apart from unmeasured differences across areas, we compare the experiences of Medicaid beneficiaries with groups that should not be affected by Medicaid payment policies. To assure that these groups are comparable to Medicaid beneficiaries, we reweight the data using propensity score methods. We use a difference‐in‐differences model to assess the effects of Medicaid payment generosity on four categories of access and use measures (continuity of care, preventive care, visits, and perceptions of provider communication and quality of care).Principal Findings. Higher payments increase the probability of having a usual source of care and the probability of having at least one visit to a doctor and other health professional for Medicaid adults, and produce more positive assessments of the health care received by adults and children. However, payment generosity has no effect on the other measures that we examined, such as the probability of receiving preventive care or the probability of having unmet needs.Conclusions. Higher payment rates can improve some aspects of access and use for Medicaid beneficiaries, but the effects are not dramatic.
Satisfaction with Surgery Outcomes and the Decision Process in a Population‐Based Sample of Women with Breast Cancer
Authors: Lantz Paula M. , Janz Nancy K. , Fagerlin Angela , Schwartz Kendra , Liu Lihua , Lakhani Indu , Salem Barbara , Katz Steven J. 
Published: May 2005

Objective. To better understand medical decision making in the context of “preference sensitive care,” we investigated factors associated with breast cancer patients' satisfaction with the type of surgery received and with the decision process.Data Sources/Data Collection. For a population‐based sample of recently diagnosed breast cancer patients in the Detroit and Los Angeles metropolitan areas (N=1,633), demographic and clinical data were obtained from the Surveillance, Epidemiology, and End Results tumor registry, and self‐reported psychosocial and satisfaction data were obtained through a mailed survey (78.4 percent response rate).Study Design. Cross‐sectional design in which multivariable logistic regression was used to identify sociodemographic and clinical factors associated with three satisfaction measures: low satisfaction with surgery type, low satisfaction with the decision process, and decision regret.Principal Findings. Overall, there were high levels of satisfaction with both surgery and the decision process, and low rates of decision regret. Ethnic minority women and those with low incomes were more likely to have low satisfaction or decision regret. In addition, the match between patient preferences regarding decision involvement and their actual level of involvement was a strong indicator of satisfaction and decision regret/ambivalence. While having less involvement than preferred was a significant indicator of low satisfaction and regret, having more involvement than preferred was also a risk factor. Women who received mastectomy without reconstruction were more likely to report low satisfaction with surgery (odds ratio [OR]=1.54, p<.05), low satisfaction with the process (OR=1.37, p<.05), and decision regret (OR=1.55, p<.05) compared with those receiving breast conserving surgery (BCS). An additional finding was that as patients' level of involvement in the decision process increased, the rate of mastectomy also increased (p<.001).Conclusions. A significant proportion of breast cancer patients experience a decision process that matches their preferences for participation, and report satisfaction with both the process and the outcome. However, women who report more involvement in the decision process are significantly less likely to receive a lumpectomy. Thus, increasing patient involvement in the decision process will not necessarily increase use of BCS or lead to greater satisfaction. The most salient aspect for satisfaction with the decision making process is the match between patients' preferences and experiences regarding participation.
Health Services for Women in Outpatient Substance Abuse Treatment
Authors: Campbell Cynthia I. , Alexander Jeffrey A. 
Published: May 2005

Objective. To evaluate how a sample of outpatient substance abuse treatment units respond to organizational and environmental influences by adopting and implementing treatment services for women.Data Sources. The National Drug Abuse Treatment System Survey from 1995 and 2000, a national survey of outpatient substance abuse treatment units.Study Design. Health services for women are the dependent variables. The predictors include organizational and environmental factors that represent resource dependence and institutional pressures for the treatment unit. Logistic regression and Heckman selection models were used to test hypotheses.Data Collection. Program directors and clinical supervisors at each treatment unit were interviewed by telephone in 1995 and 2000.Principal Findings. Units that depended on specific funding for women's programs and that depended on government funds were more likely to adopt, but not necessarily implement, women's services. Methadone units and units that train more staff to work with women were more likely to adopt as well as implement women's services. Private not‐for‐profit units were more likely to adopt some services, while for‐profit units were less so. However, in general, neither for‐profit nor not‐for‐profit units significantly implemented services. There was evidence that the odds of adopting services were greater in 2000 than 1995 for two services, but were otherwise stable.Conclusions. There is considerable variation in the adoption and implementation of women's services. In addition, not all adopted services were significantly implemented, which could reflect limited organizational resources and/or conflicting expectations. This also suggests that referral mechanisms to these services, and therefore access, may not be adequate. Government funds and specific funds for women's programs are important resources for the provision of these services. Women's services appear more available in methadone units, suggesting that regulation has been influential and that the recent methadone accreditation system should be evaluated. Staff training may be one strategy to encourage implementation of these services. For the most part, the adoption of services for women did not change between 1995 and 2000.
Do Seniors Understand Their Risk of Moving to a Nursing Home?
Authors: Taylor Donald H. , Osterman Jan , Will Acuff S. , Østbye Truls 
Published: May 2005

Objective. To determine whether seniors understand their risk of moving to a nursing home.Data Sources. We used longitudinal data from the Asset and Health Dynamics Among the Oldest Old (AHEAD) database. AHEAD is a nationally representative survey (n=8,203) of community dwellers aged 70+ years and their spouses.Study Design. We followed respondents for 5 years from the date of the first interview fielded in 1993. Our primary dependent variable was whether respondents moved to a nursing home within 5 years of baseline; self‐assessed probability of moving to a nursing home within 5 years, also assessed at baseline, was the primary explanatory variable.Principal Findings. We found that seniors who believed they were more likely to move to a nursing home within 5 years were indeed more likely to do so, and that most elders overestimated their likelihood of moving to a nursing home.Conclusions. Low rates of private long‐term care insurance are not plausibly a result of seniors underestimating their personal risk of moving to a nursing home; such an assumption is inherent in many strategies to plan for the future long‐term care needs of the baby boom generation.
Not of One Mind: Mental Models of Clinical Practice Guidelines in the Veterans Health Administration
Authors: Hysong Sylvia J. , Best Richard G. , Pugh Jacqueline A. , Moore Frank I. 
Published: May 2005

Objective.The purpose of this paper is to present differences in mental models of clinical practice guidelines (CPGs) among 15 Veterans Health Administration (VHA) facilities throughout the United States.Data Sources.Two hundred and forty‐four employees from 15 different VHA facilities across four service networks around the country were invited to participate. Participants were selected from different levels throughout each service setting from primary care personnel to facility leadership.Study Design.This qualitative study used purposive sampling, a semistructured interview process for data collection, and grounded theory techniques for analysis.Data Collection.A semistructured interview was used to collect information on participants' mental models of CPGs, as well as implementation strategies and barriers in their facility.Findings.Analysis of these interviews using grounded theory techniques indicated that there was wide variability in employees' mental models of CPGs. Findings also indicated that high‐performing facilities exhibited both (a) a clear, focused shared mental model of guidelines and (b) a tendency to use performance feedback as a learning opportunity, thus suggesting that a shared mental model is a necessary but not sufficient step toward successful guideline implementation.Conclusions.We conclude that a clear shared mental model of guidelines, in combination with a learning orientation toward feedback are important components for successful guideline implementation and improved quality of care.
Imputation of SF‐12 Health Scores for Respondents with Partially Missing Data
Authors: Liu Honghu , Hays Ron D. , Adams John L. , Chen Wen‐Pin , Tisnado Diana , Mangione Carol M. , Damberg Cheryl L. , Kahn Katherine L. 
Published: May 2005

Objective. To create an efficient imputation algorithm for imputing the SF‐12 physical component summary (PCS) and mental component summary (MCS) scores when patients have one to eleven SF‐12 items missing.Study Setting. Primary data collection was performed between 1996 and 1998.Study Design. Multi‐pattern regression was conducted to impute the scores using only available SF‐12 items (simple model), and then supplemented by demographics, smoking status and comorbidity (enhanced model) to increase the accuracy. A cut point of missing SF‐12 items was determined for using the simple or the enhanced model. The algorithm was validated through simulation.Data Collection. Thirty‐thousand‐three‐hundred and eight patients from 63 physician groups were surveyed for a quality of care study in 1996, which collected the SF‐12 and other information. The patients were classified as “chronic” patients if they reported that they had diabetes, heart disease, asthma/chronic obstructive pulmonary disease, or low back pain. A follow‐up survey was conducted in 1998.Principal Findings. Thirty‐one percent of the patients missed at least one SF‐12 item. Means of variance of prediction and standard errors of the mean imputed scores increased with the number of missing SF‐12 items. Correlations between the observed and the imputed scores derived from the enhanced models were consistently higher than those derived from the simple model and the increments were significant for patients with ≥6 missing SF‐12 items (p<.03).Conclusion. Missing SF‐12 items are prevalent and lead to reduced analytical power. Regression‐based multi‐pattern imputation using the available SF‐12 items is efficient and can produce good estimates of the scores. The enhancement from the additional patient information can significantly improve the accuracy of the imputed scores for patients with ≥6 items missing, leading to estimated scores that are as accurate as that of patients with <6 missing items.