摘要:

AbstractAn issue of continuing interest is the interpretation and reporting of ‘negative’ studies, namely studies that do not find statistically significant differences. The most common approach is the design‐power method which determines, irrespective of the observed difference, what differences the studycouldhave been expected to detect. We propose an alternative approach, the application of equivalence testing methods, where we define equivalence to mean that the actual difference lies within some specified limits. This approach, in contrast to the design‐power approach, provides a way of quantifying (withp‐values) what was actually determined from the study instead of saying what the study may or may not have accomplished with some degree of certainty (power). For example, a possible outcome of the equivalence testing approach is the conclusion at the 5 per cent level that two means (or proportions) do not differ by more than some specified amount.The equivalence testing approach applies toanystudy design. We illustrate the method with a cancer clinical trial and an epidemiologic case‐control study. In addition, for those studies in which one cannot specify limitsa priori, we propose the use of equivalence curves to summarize and present the st

ISSN:0277-6715    

DOI:10.1002/sim.4780050302

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

年代:1986

数据来源: WILEY

摘要:

AbstractWe discuss the advantages and problems of using sequential allocation procedures for assigning treatments in a clinical trial. We use Monte Carlo methods to study the exact distribution of the fourfold chi‐squared statistic for the case of no stratifying variables except sequence of entry. We display situations in which the distribution is well‐approximated by the chi‐squared distribution or by Efron's adjusted chi‐squared and situations where these approximations fail. We provide suggestions for recognition and handling of situations in which both approach

ISSN:0277-6715    

DOI:10.1002/sim.4780050303

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

年代:1986

数据来源: WILEY

摘要:

AbstractA trial of Duchenne muscular dystrophy involved tracking boys of all ages through a one‐year baseline period, followed by a one‐year trial of leucine versus placebo treatment. In this paper we develop a model for a total‐muscle‐strength score that uses the data of the extended baseline period in the evaluation of the leucine treatment. The model is based on a polynomial growth curve in age whose coefficients can vary according to treatment or phase. Maximum likelihood estimates of the parameters of the model are obtained from use of the EM algorithm. We propose tests for the adequacy of the model as well as for treatment effects. A quadratic model appears the most parsimonious fit to the data and there is no evidence of any leucine effect on scores. We examine the asymptotic power of the test for treatment effect and compare it with that of a simpler a

ISSN:0277-6715    

DOI:10.1002/sim.4780050304

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

年代:1986

数据来源: WILEY

摘要:

AbstractA statistical analysis is presented of the intensities of admissions to psychiatric hospitals among women in Denmark who either gave birth to a child in the year 1975 or had an induced abortion in the same year. The models used are time‐continuous Markov and semi‐Markov processes, and the methods employed include non‐parametric and semi‐parametric analysis of counting processes. The influence of prior psychiatric admissions on the choice of terminating the pregnancy with an induced abortion is also

ISSN:0277-6715    

DOI:10.1002/sim.4780050305

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe mean or median of the follow‐up times as a measure of the quality or completeness of the follow‐up in a survival analysis can sometimes be misleading—a more severe disease will have shorter follow‐up times because of earlier deaths. We suggest here that estimates of the censoring distribution provide a more useful measure of the follow‐up. This paper gives estimation procedures for both grouped‐time (cohort) data and continuous data, and provides an

ISSN:0277-6715    

DOI:10.1002/sim.4780050306

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

年代:1986

数据来源: WILEY

摘要:

AbstractWe outline the methods of Bayesian inference for applications to case‐control studies. These methods appear as the natural way of making inferences, since much of the controversy that surrounds a specific case‐control study is subjective. We derive conjugate prior distributions of exposure, posterior distributions of the ratio of the odds of being incident with a disease both with and without exposure to a potential causal agent, and convenient approximations. In particular, we show how one may carry out ‘case‐control studies’ without necessarily having a control group. We illustrate these ideas with the data that first showed the relationship betweenin uteroexposure to diethylstilbestrol and cancer of the vagina in yo

ISSN:0277-6715    

DOI:10.1002/sim.4780050307

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

年代:1986

数据来源: WILEY

摘要:

AbstractIn investigating an epidemic or outbreak of a disease in which patient contact (appropriately defined) is hypothesized to be a factor, investigators may ask patients to provide names of people with whom they have had contact. This paper provides statistical methods for assessing whether or not the number of named contacts who are themselves cases is significantly large. Survey data on the epidemiology of acquired immune deficiency syndrome illustrate the methods.

ISSN:0277-6715    

DOI:10.1002/sim.4780050308

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

年代:1986

数据来源: WILEY

摘要:

AbstractThis paper considers statistical power properties of a test of whether a disease is caused by a recessive gene, using data on HLA sharing properties of affected sibs. It is found that the test has very poor power characteristics, and in particular we are sometimes just as likely to accept the hypothesis that the gene is recessive when it is dominant as when it is truly recessive.

ISSN:0277-6715    

DOI:10.1002/sim.4780050309

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

年代:1986

数据来源: WILEY

ISSN:0277-6715    

DOI:10.1002/sim.4780050310

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

年代:1986

数据来源: WILEY

ISSN:0277-6715    

DOI:10.1002/sim.4780050311

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

年代:1986

数据来源: WILEY