Abstract:
:Blinded estimation of variance allows for changing the sample size without compromising the integrity of the trial. Some of the methods that estimate the variance in a blinded manner either make untenable assumptions or are only applicable to two-treatment trials. We propose a new method for continuous endpoints that makes minimal assumptions. The method uses the enrollment order of subjects and the randomization block size to estimate the variance. It can be applied to normal or non-normal data, trials with two or more treatments, equal or unequal allocation schemes, fixed or random randomization block sizes, and single or multi-centre trials. The variance estimator is unbiased and performs best when the randomization block size is the smallest. Simulation results suggest that for many commonly used randomization block sizes the proposed estimator is expected to perform well. The proposed method is used to estimate the variance of the endpoint for two trials and is shown to perform well by comparison with its unblinded counterpart.
journal_name
Stat Medjournal_title
Statistics in medicineauthors
Xing B,Ganju Jdoi
10.1002/sim.2070subject
Has Abstractpub_date
2005-06-30 00:00:00pages
1807-14issue
12eissn
0277-6715issn
1097-0258journal_volume
24pub_type
杂志文章abstract::Three-arm trials including the experimental treatment, an active reference treatment and a placebo are recommended in the guidelines of the ICH and EMEA/CPMP as a useful approach to the assessment of assay sensitivity. Generally, the acceptable non-inferiority margin Δ has been defined as the maximum clinically irrele...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.4099
更新日期:2011-02-10 00:00:00
abstract::Drop-out often occurs in clinical trials with multiple visits and drop-out is often informative in the sense that the population of patients who dropped out is different from the population of patients who completed the study. To handle data with informative drop-out, an intention-to-treat analysis, which evaluates tr...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.1519
更新日期:2003-08-15 00:00:00
abstract::Patient non-compliance and drop-out can bias analyses of clinical trial data. I describe a parametric model for treatment cross-over and drop-out and demonstrate how the concept of ignorability, originally defined for incomplete-data problems, can elucidate sources of bias in clinical trials. I discuss some implicatio...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/(sici)1097-0258(19990915/30)18:17/18<2421:
更新日期:1999-09-15 00:00:00
abstract::The National Children's Study is a national household probability sample designed to identify 100,000 children at birth and follow the sampled children for 21 years. Data from the study will support examining numerous hypotheses concerning genetic and environmental effects on the health and development of children. Th...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.3891
更新日期:2010-06-15 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 identification of changes in the recent trend is an important issue in the analysis of cancer mortality and incidence data. We apply a joinpoint regression model to describe such continuous changes and use the grid-search method to fit the regression function with unknown joinpoints assuming constant variance and ...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/(sici)1097-0258(20000215)19:3<335::aid-sim
更新日期:2000-02-15 00:00:00
abstract::The Cardiac Arrythmia Suppression Trial was stopped much earlier than planned. Statistical considerations played a very important role in the decision. Flexible group sequential testing was developed for the trial by implementing a Lan and DeMets procedure with use of the permutation test. We compute P-values from the...
journal_title:Statistics in medicine
pub_type: 临床试验,杂志文章,多中心研究,随机对照试验
doi:10.1002/sim.4780090915
更新日期:1990-09-01 00:00:00
abstract::In some randomized controlled trials, subjects with a better prognosis may be diverted into the treatment group. This subverting of randomization results in an unobserved non-compliance with the originally intended treatment assignment. Consequently, the estimate of treatment effect from these trials may be biased. Th...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.715
更新日期:2001-02-28 00:00:00
abstract::We propose a joint modeling approach to investigating the observed and latent risk factors of mixed types of outcomes. The proposed model comprises three parts. The first part is an exploratory factor analysis model that summarizes latent factors through multiple observed variables. The second part is a proportional h...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.8840
更新日期:2020-12-09 00:00:00
abstract::We propose the use of Gaussian mixed models to analyse statistically 24 hour ambulatory blood pressure data from clinical trials. We develop specific models and apply them to data from a clinical study that compares two angiotensin-converting enzyme inhibitors. We investigate and discuss computing issues related to th...
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.4780121803
更新日期:1993-09-30 00:00:00
abstract::Providing personalized treatments designed to maximize benefits and minimizing harms is of tremendous current medical interest. One problem in this area is the evaluation of the interaction between the treatment and other predictor variables. Treatment effects in subgroups having the same direction but different magni...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.5429
更新日期:2012-12-10 00:00:00
abstract::This paper assesses the coverage probability of commonly used confidence intervals for the standardized mortality ratio (SMR) when death certificates are missing. It also proposes alternative confidence interval approaches with coverage probabilities close to .95. In epidemiology, the SMR is an important measure of ri...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.7432
更新日期:2017-11-30 00:00:00
abstract::We present a new approach to training back-propagation artificial neural nets (BP-ANN) based on regularization and cross-validation and on initialization by a logistic regression (LR) model. The new approach is expected to produce a BP-ANN predictor at least as good as the LR-based one. We have applied the approach to...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.1107
更新日期:2002-05-15 00:00:00
abstract::A mixed effect model is proposed to jointly analyze multivariate longitudinal data with continuous, proportion, count, and binary responses. The association of the variables is modeled through the correlation of random effects. We use a quasi-likelihood type approximation for nonlinear variables and transform the prop...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.7401
更新日期:2017-11-10 00:00:00
abstract::Treatment effects for multiple outcomes can be meta-analyzed separately or jointly, but no systematic empirical comparison of the two approaches exists. From the Cochrane Library of Systematic Reviews, we identified 45 reviews, including 1473 trials and 258,675 patients, that contained two or three univariate meta-ana...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.6044
更新日期:2014-04-30 00:00:00
abstract::We survey models for analysing repeated observations on an ordered categorical response variable. The models presented are univariate models that permit correlation among repeated measurements. The models describe simultaneously the dependence of marginal response distributions on values of explanatory variables and o...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.4780081005
更新日期:1989-10-01 00:00:00
abstract::Multi-type recurrent event data arise when two or more different kinds of events may occur repeatedly over a period of observation. The scientific objectives in such settings are often to describe features of the marginal processes and to study the association between the different types of events. Interval-censored m...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.1936
更新日期:2005-03-15 00:00:00
abstract::I derive the locally most powerful rank tests for acceleration against semi-parametric alternatives when some patients are cured of the disease. I consider some particular classes of alternatives and present simulation results to verify the validity of the proposed tests. Real data from clinical trials for childhood l...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.4780141905
更新日期:1995-10-15 00:00:00
abstract::The coefficient of individual equivalence is a permutation-based measure of agreement between two observers making replicated readings on each subject. It compares the observed disagreement between the observers to the expected disagreement under individual equivalence. Individual equivalence of observers requires tha...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.5323
更新日期:2012-09-10 00:00:00
abstract::Box-Cox transformation is investigated for regression models for left-censored data. Examples are provided using coronary calcification data from the Multi-Ethnic Study of Atherosclerosis and pharmacokinetic data of a nicotine nasal spray. ...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.1925
更新日期:2004-12-15 00:00:00
abstract::We consider recurrent events of the same type that occur during alternating restraint and non-restraint time periods. This research is motivated by a study on juvenile recidivism, where the probationers were followed for re-offenses during alternating placement periods and free-time periods. During the placement perio...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.7150
更新日期:2017-02-20 00:00:00
abstract::Although radical changes in drug regulation are rare (e.g., the Federal Food, Drug and Cosmetic Act of 1938 and the 1962 amendment to the Act creating an effectiveness requirement), regulations and guidance do evolve significantly in the face of new problems and accumulating experience. Recent changes have been driven...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.1298
更新日期:2002-10-15 00:00:00
abstract::Funnel plots are widely used to visualize grouped data, for example, in institutional comparison. This paper extends the concept to a multi-level setting, displaying one level at a time, adjusted for the other levels, as well as for covariates at all levels. These level-adjusted funnel plots are based on a Markov chai...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.5677
更新日期:2014-09-20 00:00:00
abstract::Combinatorial drugs have been widely applied in disease treatment, especially chemotherapy for cancer, due to its improved efficacy and reduced toxicity compared with individual drugs. The study of combinatorial drugs requires efficient experimental designs and proper follow-up statistical modeling techniques. Linear ...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.7971
更新日期:2019-01-30 00:00:00
abstract::A Non-Parametric Maximum Likelihood approach to the estimation of relative risks in the context of disease mapping is discussed and a NPML approximation to conditional autoregressive models is proposed. NPML estimates have been compared to other proposed solutions (Maximum Likelihood via Monte Carlo Scoring, Hierarchi...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/1097-0258(20000915/30)19:17/18<2539::aid-s
更新日期:2000-09-15 00:00:00
abstract::We review two recent trends: the emergence of evidence-based medicine and the growing use of Bayesian statistics in medical applications. Evidence-based medicine requires an integrated assessment of the available evidence, and associated uncertainty, but there is also an emphasis on decision-making, for individual pat...
journal_title:Statistics in medicine
pub_type: 杂志文章,评审
doi:10.1002/1097-0258(20001215)19:23<3291::aid-sim627>
更新日期:2000-12-15 00:00:00
abstract::Lung function tests are used both clinically, in assessing disease, and epidemiologically, in identifying those factors which influence the growth and aging process of the lungs. The user must beware of several common pitfalls in the use of these tests, however. First, the commonly used tests of lung function can only...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.4780070106
更新日期:1988-01-01 00:00:00
abstract::This paper considers the problem of selecting a set of regressors when the response variable is distributed according to a specified parametric model and observations are censored. Under a Bayesian perspective, the most widely used tools are Bayes factors (BFs), which are undefined when improper priors are used. In or...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.6249
更新日期:2014-11-20 00:00:00
abstract::A personalized treatment strategy formalizes evidence-based treatment selection by mapping patient information to a recommended treatment. Personalized treatment strategies can produce better patient outcomes while reducing cost and treatment burden. Thus, among clinical and intervention scientists, there is a growing...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.6783
更新日期:2016-04-15 00:00:00
abstract::The relative concentration index (RCI) and the absolute concentration index (ACI) have been widely used for monitoring health disparities with ranked health determinants. The RCI has been extended to allow value judgments about inequality aversion by Pereira in 1998 and by Wagstaff in 2002. Previous studies of the ext...
journal_title:Statistics in medicine
pub_type: 杂志文章
doi:10.1002/sim.7952
更新日期:2019-01-15 00:00:00