ISSN:0277-6715    

DOI:10.1002/sim.4780110102

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

年代:1992

数据来源: WILEY

摘要:

AbstractA screening design was used in a trial that compared a standard regimen to five experimental regimens for the treatment of advanced colorectal cancer where the endpoint was survival. The two‐stage design permitted the termination of accrual to experimental regimens that failed to show promise at the first stage. It also allowed for termination of accrual to the standard regimen if an experimental regimen appeared to offer a highly significant improvement over the standard regimen. This paper presents a description of the design and the results of the tria

ISSN:0277-6715    

DOI:10.1002/sim.4780110103

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

年代:1992

数据来源: WILEY

摘要:

AbstractSubset analysis is the examination of treatment comparisons within groups of patients with restricted levels of patient characteristics. Such analyses are vulnerable to multiplicity effects. We examine the problem in the context of a proportional hazards model with terms for treatment, each of several dichotomous covariates representing the patient characteristics of interest, and treatment‐by‐covariate interaction effects. Parametrically, a subset‐specific treatment effect is equal to the treatment effect term plus a linear combination of the interaction terms. We present Bayesian point and interval estimates under the assumption that the interaction terms are exchangeable and the prior distributions for the other regression parameters are locally uniform. This produces a shrinking of the estimated interaction effects towards zero, thereby discounting them and dealing in a natural way with multiplicity. We illustrate the method using results of a recent North Central Cancer Treatment Group/Mayo Clinic study in advanced colorectal c

ISSN:0277-6715    

DOI:10.1002/sim.4780110104

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

年代:1992

数据来源: WILEY

摘要:

AbstractWe describe the application of Bayesian methods to the monitoring and analysis of a trial of treatment for patients with advanced colorectal carcinoma. We discuss the choice of prior distribution and justify the use of a truncated normal distribution with a probability mass at zero difference. The stopping rule, based on the trials of the posterior distribution and a chosen range of equivalence, yields an upper boundary very close to the Pocock group sequential boundary. The Bayes stopping rule is quite sensitive to the amount of probability mass at zero in the prior distribution.

ISSN:0277-6715    

DOI:10.1002/sim.4780110105

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe NCCTG randomized controlled clinical trial for the treatment of avanced colorectal carcinoma is a wonderful case study of the dynamic interplay between scientific learning and statistical inference. Ethical concerns for minimizing the number of patients assigned to an inferior treatment and interest in identifying subsets of patients for whom a treatment is most likely efficacious pose challenging problems for the practice of statistics. In the first part of this paper, I comment on the applications of Bayesian methods to these problems in the NCCTG trial as presented by Freedman and Spieglehalter and Dixon and Simon, respectively. In the second part of this paper, I discuss and illustrate a Bayesian approach to model sensitivity analysis with a particular focus on model specification and criticism. The Bayesian approach provides a formal methodology to assess the sensitivity of inferences to the inputs into an analysis so that it is possible to investigate the consequences of the specification of the model. I apply these methods to the specification and criticism of a class of survival models for the analysis of survival times in the NCCTG trial.

ISSN:0277-6715    

DOI:10.1002/sim.4780110106

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

年代:1992

数据来源: WILEY

摘要:

AbstractMonitoring clinical trials often requires examining the interim findings to see if the sample size originally specified in the protocol will provide the required power against the null hypothesis when the alternative hypothesis is true, and to increase the sample size if necessary. This paper presents a new method, based on the overall response rate, for carrying out interim power evaluations when the observations have binomial distributions, without unblinding the treatment assignments or materially affecting the type I error rate. Simulation study results confirm the performance of the method.

ISSN:0277-6715    

DOI:10.1002/sim.4780110107

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

年代:1992

数据来源: WILEY

摘要:

AbstractThis paper provides an annotated bibliography of over 100 articles concerning methods for analysing correlated categorical response data. Most of the papers listed here concern categorical regression models and estimation, with particular emphasis on binary responses. The papers are classified by several characteristics which group them according to common themes. The bibliography serves as a reference of methods for analysts of correlated categorical data, as well as for persons interested in methodologic work in this active area of statistical research.

ISSN:0277-6715    

DOI:10.1002/sim.4780110108

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

年代:1992

数据来源: WILEY

摘要:

AbstractThis article uses log‐linear models to describe pairwise agreement among several raters who classify a sample on a subjective categorical scale. The models describe agreement structure simultaneously for second‐order marginal tables of a multidimensional cross‐classification of ratings. Practical difficulties arise in fitting the models, because models refer to pairwise marginal tables of a very large and sparse table. A standard analysis that treats the marginal tables as independent yields consistent estimates of model parameters, but not of the covariance matrix of the estimates. We estimate the covariance matrix using the jackknife. We apply the models to describe agreement between evaluations made by seven pathologists of carcinomain situof the uterine cervix, using a five‐level ordinal scale. Previous analyses showed differences among the pathologists in their pairwise levels of agreement, but we observe near homogeneity in the dependence structure of their

ISSN:0277-6715    

DOI:10.1002/sim.4780110109

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

年代:1992

数据来源: WILEY

摘要:

AbstractMultivariate data are difficult to analyse partly because of difficulty in looking at the data. Repeated measures data have a special structure that makes the parallel plot1,2particularly effective for viewing the data. In this paper we use parallel plots to display not just raw data but also residuals from standard models fit to repeated measures data. The plots are useful for determining how well a particular model fits the data, identifying outlying observations and suggesting terms missing from the linear predictor.

ISSN:0277-6715    

DOI:10.1002/sim.4780110110

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

年代:1992

数据来源: WILEY

摘要:

AbstractHeart rate variability and heart period variability are important indicators of the functioning of the autonomic nervous system and are strong predictors of survival after myocardial infarction. The standard deviation of a patient's series of normal heart periods (consecutive normal RR intervals) is positively and, in some populations, strongly correlated with the mean period length. This phenomenon has led some investigators to use the coefficient of variation as their measure of variability, because it correlates less strongly with the mean period length. Using data from a multicentre post‐infarction natural history study, we show that the standard deviation of the instantaneous heart rates has, like the coefficient of variation, only a modest correlation with the mean period length. Unlike the coefficient of variation, however, this standard deviation is derivable from established statistical principles. We show further that the coefficient of variation, the standard deviation of heart rates, and the standard deviation of heart periods are approximately equally strong predictors of survival after myocardial infarctio

ISSN:0277-6715    

DOI:10.1002/sim.4780110111

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

年代:1992

数据来源: WILEY