摘要:

AbstractIn most randomized clinical trials not all patients adhere to the therapy to which they were randomly assigned. Instead, they may receive the therapy assigned to another treatment group, or a therapy different from any prescribed in the protocol. When non‐adherence occurs, problems occur with the analysis comparing the treatments under study. Rigorous statistical principles require attributing outcome events to the original random treatment assignment (‘intent‐to‐treat’ analysis). Using data from the Veterans Administration Cooperative Study of Coronary Artery Bypass Surgery, we report the intent‐to‐treat analysis and apply four other methods of analysis for analysing non‐adherers: 1. exclude non‐adherers from analysis; 2. transfer them to the alternative treatment group at the time of randomization; 3. censor them at the time of treatment change, and 4. transfer them to the alternative treatment group at the time of treatment change. Inherent problems and biases of these four other meth

ISSN:0277-6715    

DOI:10.1002/sim.4780121302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractWe address the problem of selecting a treatment for phase II evaluation when several candidate treatments emerging from phase I testing are available. A pre‐phase II Bayesian selection design which randomizes patients among treatments is proposed. The patient group in the trial has prognosis more favourable than that of phase I patients but less favourable than the target group of the subsequent phase II trial. The patient response rate distribution in each treatment arm is continually updated during the trial for comparison with early termination cutoffs, and the best final treatment must satisfy a minimal posterior efficacy criterion. The primary aim is to replace the usual informal treatment selection process with a fair comparison formally based on a combination of prior opinion and clinical dat

ISSN:0277-6715    

DOI:10.1002/sim.4780121303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractStatistical analysis of difference between groups in change for some variable, adjusting for initial value, is complicated by the presence of intra‐individual variation in that variable. We estimate here the asymptotic bais that results from calculating the adjusted between‐group difference by ordinary least squares (OLS) from observed data. We also present explicit formulae that use the OLS estimates, the difference between treatment groups in mean initial values, and a measure of the intra‐individual variation to compute a corrected estimator and its variance. Alternatively, we can use OLS on transformed data to obtain unbiased estimates, in which we replace initial observed values by conditional Stein estimates of true values. We illustrate the results with data from an observational study and a clinical

ISSN:0277-6715    

DOI:10.1002/sim.4780121304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

Abstract‘Qualitative’ or ‘crossover’ interactions arise when a new treatment, compared with a control treatment, is beneficial in some subsets of patients and harmful in other subsets. We present a new range test for crossover interactions and compare it with the likelihood ratio test developed by Gail and Simon. The range test has greater power when the new treatment is harmful in only a few subsets, whereas the likelihood ratio test has greater power when the new treatment is harmful in several subsets. We provide power tables for both tests to facilitate sample size calculations for designing experiments to detect qualitative interactions and for interpreting the results of clinical

ISSN:0277-6715    

DOI:10.1002/sim.4780121305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThis paper discusses a new method which allows the extraction of a background disease rate from a data set consisting of spatial co‐ordinates of morbidity or mortality events. We demonstrate its application with two data sets, one based on cancer registry data and the other on death certificate

ISSN:0277-6715    

DOI:10.1002/sim.4780121306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractDependent data, such as arise with cluster sampling, typically yield variances of parameter estimates which are larger than would be provided by a simple random sample of the same size. This variance inflation factor is called the design effect of the estimator. Design effects have been derived for cluster sampling designs using simple estimators such as means and proportions, and also for linear regression coefficient estimators. In this paper, we show that a method to derive design effects for linear regression estimators extends to generalized linear models for binary responses. In particular, some simple expressions for design effects in the linear regression model provide accurate approximations for binary regression models such as those based on the logistic, probit and complementary log—log links. We corroborate our findings with two examples and some simulation studie

ISSN:0277-6715    

DOI:10.1002/sim.4780121307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

ISSN:0277-6715    

DOI:10.1002/sim.4780121308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

ISSN:0277-6715    

DOI:10.1002/sim.4780121309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

ISSN:0277-6715    

DOI:10.1002/sim.4780121310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

ISSN:0277-6715    

DOI:10.1002/sim.4780121311

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY