Abstract:
:We discuss some of the fundamental concepts underlying the development of frailty and random effects models in survival. One of these fundamental concepts was the idea of a frailty model where each subject has his or her own disposition to failure, their so-called frailty, additional to any effects we wish to quantify via regression. Although the concept of individual frailty can be of value when thinking about how data arise or when interpreting parameter estimates in the context of a fitted model, we argue that the concept is of limited practical value. Individual random effects (frailties), whenever detected, can be made to disappear by elementary model transformation. In consequence, unless we are to take some model form as unassailable, beyond challenge and carved in stone, and if we are to understand the term 'frailty' as referring to individual random effects, then frailty models have no value. Random effects models on the other hand, in which groups of individuals share some common effect, can be used to advantage. Even in this case however, if we are prepared to sacrifice some efficiency, we can avoid complex modelling by using the considerable power already provided by the stratified proportional hazards model. Stratified models and random effects models can both be seen to be particular cases of partially proportional hazards models, a view that gives further insight. The added structure of a random effects model, viewed as a stratified proportional hazards model with some added distributional constraints, will, for group sizes of five or more, provide no more than modest efficiency gains, even when the additional assumptions are exactly true. On the other hand, for moderate to large numbers of very small groups, of sizes two or three, the study of twins being a well known example, the efficiency gains of the random effects model can be far from negligible. For such applications, the case for using random effects models rather than the stratified model is strong. This is especially so in view of the good robustness properties of random effects models. Nonetheless, the simpler analysis, based upon the stratified model, remains valid, albeit making a less efficient use of resources.
journal_name
Stat Medjournal_title
Statistics in medicineauthors
O'Quigley J,Stare Jdoi
10.1002/sim.1259subject
Has Abstractpub_date
2002-11-15 00:00:00pages
3219-33issue
21eissn
0277-6715issn
1097-0258journal_volume
21pub_type
杂志文章abstract::The validity and practical utility of observational medical research depends critically on good study design, excellent data quality, appropriate statistical methods and accurate interpretation of results. Statistical methodology has seen substantial development in recent times. Unfortunately, many of these methodolog...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.6265
更新日期:2014-12-30 00:00:00
abstract::The statistical analysis of panel count data has recently attracted a great deal of attention, and a number of approaches have been developed. However, most of these approaches are for situations where the observation and follow-up processes are independent of the underlying recurrent event process unconditional or co...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.5724
更新日期:2013-07-30 00:00:00
abstract::In vitro fertilization (IVF) is an increasingly common method of assisted reproductive technology. Because of the careful observation and follow-up required as part of the procedure, IVF studies provide an ideal opportunity to identify and assess clinical and demographic factors along with environmental exposures that...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.6050
更新日期:2014-05-10 00:00:00
abstract::Current methods for statistical analysis of twin studies focus on continuous and dichotomous data, while only limited methodology exists for analysing multinomial data. As a consequence, investigators are often tempted to collapse multinomial data into two categories simply to facilitate the analysis. We address this ...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/1097-0258(20010130)20:2<249::aid-sim641>3.
更新日期:2001-01-30 00:00:00
abstract::We estimate a Cox proportional hazards model where one of the covariates measures the level of a subject's cognitive functioning by grading the total score obtained by the subject on the items of a questionnaire. A case study is presented where the sample includes partial respondents, who did not answer some questionn...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.3773
更新日期:2010-01-30 00:00:00
abstract::Correlation is inherent in longitudinal studies due to the repeated measurements on subjects, as well as due to time-dependent covariates in the study. In the National Longitudinal Study of Adolescent to Adult Health (Add Health), data were repeatedly collected on children in grades 7-12 across four waves. Thus, obser...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.8099
更新日期:2019-05-30 00:00:00
abstract::It is naive and incorrect to use the proportions of successful operations to compare the performance of surgeons because the patients' risk profiles are different. In this paper, we explore the use of risk-adjusted procedures to compare the performance of surgeons. One such risk-adjusted statistic is the standardized ...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.7310
更新日期:2017-07-20 00:00:00
abstract::In this paper, we discuss family-based association test (FBATs) relating genetic data to survival and time-to-onset data. We show how the standard logrank and Wilcoxon statistics can be used with family data to develop tests of association. We prove that the FBAT-logrank approach can be identical to the proportional h...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.1707
更新日期:2004-01-30 00:00:00
abstract::Medical costs data with administratively censored observations often arise in cost-effectiveness studies of treatments for life-threatening diseases. Mean of medical costs incurred from the start of a treatment until death or a certain time point after the implementation of treatment is frequently of interest. In many...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.1556
更新日期:2004-11-15 00:00:00
abstract::Korn and Whittemore have presented methods for analyzing longitudinal data where the number of observations per individual is large relative to the number of variables considered for each subject. However, this is often not the case in epidemiologic studies, since one usually collects data at relatively few time point...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.4780040407
更新日期:1985-10-01 00:00:00
abstract::This paper gives a standard error for Cohen's Kappa, conditional on the margins of the observed r x r table. An explicit formula is given for the 2 x 2 table, and a procedure for the more general situation. A parsimonious log-linear model is suggested for the general case and an approximate confidence interval for kap...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.4780100512
更新日期:1991-05-01 00:00:00
abstract::This paper discusses design considerations and the role of randomization-based inference in randomized community intervention trials. We stress that longitudinal follow-up of cohorts within communities often yields useful information on the effects of intervention on individuals, whereas cross-sectional surveys can us...
journal_title:Statistics in medicine
pub_type: 杂志文章,评审
doi:10.1002/(SICI)1097-0258(19960615)15:11<1069::AID-S
更新日期:1996-06-15 00:00:00
abstract::Clinical prediction models (CPMs) can inform decision making about treatment initiation, which requires predicted risks assuming no treatment is given. However, this is challenging since CPMs are usually derived using data sets where patients received treatment, often initiated postbaseline as "treatment drop-ins." Th...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.7913
更新日期:2018-12-10 00:00:00
abstract::Quality of life (QOL) assessment is a key component of many clinical studies and frequently requires the use of single global summary measures that capture the overall balance of findings from a potentially wide-ranging assessment of QOL issues. We propose and evaluate an irregular multilevel latent variable model sui...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.4455
更新日期:2012-05-20 00:00:00
abstract::Multistate models are increasingly being used to model complex disease profiles. By modelling transitions between disease states, accounting for competing events at each transition, we can gain a much richer understanding of patient trajectories and how risk factors impact over the entire disease pathway. In this arti...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.7448
更新日期:2017-12-20 00:00:00
abstract::Cox proportional hazard regression model is a popular tool to analyze the relationship between a censored lifetime variable with other relevant factors. The semiparametric Cox model is widely used to study different types of data arising from applied disciplines such as medical science, biology, and reliability studie...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.8377
更新日期:2019-11-30 00:00:00
abstract::The design of a cross-sectional survey to estimate the age-specific incidence of an irreversible disease is considered, where the incidence rate is not changing over time and the risk of mortality is not affected by the onset of disease. The sample is assumed to give information on the current age and disease status o...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.4780132208
更新日期:1994-11-30 00:00:00
abstract::Previous work on the consequences of regression to the mean for the interpretation of responses to treatment is extended to the situation where the response measured is the proportional change in some variable. Methods for correcting for the bias are discussed. ...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.4780060203
更新日期:1987-03-01 00:00:00
abstract::The incremental life expectancy, defined as the difference in mean survival times between two treatment groups, is a crucial quantity of interest in cost-effectiveness analyses. Usually, this quantity is very difficult to estimate from censored survival data with a limited follow-up period. The paper develops estimati...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.6951
更新日期:2016-09-10 00:00:00
abstract::Conditional power (CP) is the probability that the final study result will be statistically significant, given the data observed thus far and a specific assumption about the pattern of the data to be observed in the remainder of the study, such as assuming the original design effect, or the effect estimated from the c...
journal_title:Statistics in medicine
pub_type: 杂志文章,评审
doi:10.1002/sim.2151
更新日期:2005-09-30 00:00:00
abstract::Random forest is a supervised learning method that combines many classification or regression trees for prediction. Here we describe an extension of the random forest method for building event risk prediction models in survival analysis with competing risks. In case of right-censored data, the event status at the pred...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.5775
更新日期:2013-08-15 00:00:00
abstract::Two features commonly exhibited by randomized trials of health promotion interventions are cluster randomization and stratification. Ignoring correlations between individuals within clusters can lead to an inflated type I error rate and hence a P-value which overstates the significance of the result. This paper compar...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.1256
更新日期:2002-12-30 00:00:00
abstract::We analyse the effect of using prevalence rates based on populations with different sizes in the power of spatial independence tests. We compare the well known spatial correlation Moran's index to three indexes obtained after adjusting for population density, one proposed by Oden, another proposed by Waldhör, and a th...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/(sici)1097-0258(19990830)18:16<2147::aid-s
更新日期:1999-08-30 00:00:00
abstract::Immigration-death models are proposed to analyse the infection dynamics in longitudinal studies of panels of heavily parasitized human hosts where parasites have been typed at regular intervals by PCR. Immigration refers to the acquisition of a new parasitic genotype, occurring at rate lambda, and death refers to the ...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.2189
更新日期:2005-11-15 00:00:00
abstract::This paper describes statistical procedures for use in an experiment that compares two handwashing protocols. The evaluation of a handwashing protocol entails collection of the wash effluent. Colony counts for the effluent reflect the number of flora removed by the wash protocol. The analysis aims to formulate and est...
journal_title:Statistics in medicine
pub_type: 临床试验,杂志文章,随机对照试验
doi:10.1002/sim.4780050412
更新日期:1986-07-01 00:00:00
abstract::Both the variation of positive responses (negative responses) among individuals and the internal correlation among responses for the same individual affect the precision of the estimate of sensitivity (specificity). To estimate the sensitivity (specificity) of a medical diagnostic test, this paper proposes a Bayesian ...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.4780081007
更新日期:1989-10-01 00:00:00
abstract::Biomarkers that predict the efficacy of treatment can potentially improve clinical outcomes and decrease medical costs by allowing treatment to be provided only to those most likely to benefit. We consider the design of a randomized clinical trial in which one objective is to evaluate a treatment selection marker. The...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.6564
更新日期:2015-11-30 00:00:00
abstract::Binary matched-pairs data occur commonly in longitudinal studies, such as in cross-over experiments. Many analyses for comparing the matched probabilities of a particular outcome do not utilize pairs having the same outcome for each observation. An example is McNemar's test. Some methodologists find this to be counter...
journal_title:Statistics in medicine
pub_type: 杂志文章,评审
doi:10.1002/sim.1589
更新日期:2004-01-15 00:00:00
abstract::Sam Greenhouse joined the Census Bureau as a clerk at an interesting time period for the agency. The first use of sampling in the decennial census occurred in 1940. There was a major expansion of the amount of data collected. The organization of the Census Bureau underwent radical changes, including the growth of the ...
journal_title:Statistics in medicine
pub_type: 传,历史文章,杂志文章
doi:10.1002/sim.1627
更新日期:2003-11-15 00:00:00
abstract::Case-control studies are prone to low power for testing gene-environment interactions (GXE) given the need for a sufficient number of individuals on each strata of disease, gene, and environment. We propose a new study design to increase power by strategically pooling biospecimens. Pooling biospecimens allows us to in...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.5357
更新日期:2012-11-20 00:00:00