摘要:

AbstractThe ‘textbook’ approach to determining sample size in a clinical trial has some fundamental weaknesses which we discuss. We describe a new predictive method which takes account of prior clinical opinion about the treatment difference. The method adopts the point of clinical equivalence (determined by interviewing the clinical participants) as the null hypothesis. Decision rules at the end of the study are based on whether the interval estimate of the treatment difference (classical or Bayesian) includes the null hypothesis. The prior distribution is used to predict the probabilities of making the decisions to use one or other treatment or to reserve final judgement. It is recommended that sample size be chosen to control the predicted probability of the last of these decisions. An example is given from a multi‐centre trial of superficial bladder c

ISSN:0277-6715    

DOI:10.1002/sim.4780050103

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

年代:1986

数据来源: WILEY

摘要:

AbstractFor the pain data analysed previously by Cox and Chuang. This paper proposes a new model that assumes monotone scores for ordered response categories. This proposed model possesses several attractive features and allows a stochastic ordering of the drugs under comparison. Such a model also provides insight regarding the ordinal scale used to classify response. Estimation of the parameters in the model is obtained by use of BMDP3R.

ISSN:0277-6715    

DOI:10.1002/sim.4780050104

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

年代:1986

数据来源: WILEY

摘要:

AbstractAssessment of the value of diagnostic indicators such as symptoms and laboratory tests results from calculation of the sensitivity and specificity of the indicators. Knowledge of the rate of occurrence of the disease allows for additional calculations of the error rates in using an indicator. These calculations are accurate only when the data on which they are based are reliable. If the diagnosis, which is used as the criterion for computing the sensitivity and specificity, is not accurate, then the resulting calculations will be in error. We show how a statistical method, latent class analysis, allows for the estimation of the characteristics of indicators even when an accurate diagnosis is unavailable. In addition, the method deals with several indicators at once, and provides a way to combine the information from all the indicators to make a diagnosis.

ISSN:0277-6715    

DOI:10.1002/sim.4780050105

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

年代:1986

数据来源: WILEY

摘要:

AbstractThis paper investigates the efficiency of using multiple controls in a case‐control study, when there is a single binary exposure variable. Specifically, we consider the asymptotic power of the Cochran1test statistic against non‐local alternatives of interest. When it is desirable to take multiple controls per case, we show that the marginal return rapidly diminishes as the number of controls per case increases. The effect is as strong, if not stronger, for non‐local alternatives as it is for local alternatives. Hence, it is rarely worth choosing more than three controls per case. We also provide a table of sample sizes necessary to achieve 80 per cent power for some odds ratios not equal to one. We extend the results to a special case when there are two binary exposure vari

ISSN:0277-6715    

DOI:10.1002/sim.4780050106

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

年代:1986

数据来源: WILEY

摘要:

AbstractDuring the last few years Box‐Jenkins models have become of increasing importance in such fields as economics and industry. They have been used for forecasting and for detecting relations between different time series. Similar applications are also relevant in epidemiology.Since many people who are concerned with the analysis of medical data are not familiar with this subject, a short non‐technical introduction to Box‐Jenkins models is given. The model‐building process is demonstrated in some detail using monthly case reports of the two seasonal endemic diseases chicken‐pox and mumps, and the relation between these two time series is investigated. It is found that both diseases may be represented by simple models which have basically the same statistical structure and that they are related at time‐lag O but not at othe

ISSN:0277-6715    

DOI:10.1002/sim.4780050107

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

年代:1986

数据来源: WILEY

摘要:

AbstractStatistical methods for characterizing risks are now well‐developed, although little attention has focussed on the problem of risk identification, as in the surveillance of adverse drug reactions or occupational cancers. In this paper we consider the analysis of studies in which one ascertains and compares cases of several disease groups in terms of exposure histories. We address the problem of adjusting each risk for the confounding effects of all the other risks in the data. Data analysis consists of multidimensional contingency tables or polychotomous logistic regression. The latter approach focuses attention on the exposure‐disease relations of primary interest rather than on those among the exposure factors and higher‐order interactions, and applies easily to many exposure variables and to continuous exposure variables. We describe a stepwise approach to selecting effects for inclusion in the model. Application to preliminary data from a study aimed at identification of hitherto unsuspected occupational carcinogens illustrates the general app

ISSN:0277-6715    

DOI:10.1002/sim.4780050108

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

年代:1986

数据来源: WILEY

摘要:

AbstractThis paper evaluates the relationships between various indices of proportional mortality, used in occupational and other settings where denominator data are unavailable. In particular, we examine the necessary conditions for validity of the proportional mortality ratio (PMR) and mortality odds ratio (MOR) as estimates of the standardized mortality ratio (SMR), in general and for the situation where one considers only a subset of deaths, with certain causes of death deleted from the data. We may exclude data in this way to avoid the inflationary effect on the PMRs for some causes of death (e.g. cancer) that results from a ‘healthy worker effect’ for other causes of death (e.g. heart disease). We find that cause‐deleted PMRs and MORs may be unbiased estimates of their corresponding SMR, and these indices appear most useful for specific hazards of employment or relatively infrequent causes of

ISSN:0277-6715    

DOI:10.1002/sim.4780050109

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

年代:1986

数据来源: WILEY

摘要:

AbstractWe assess stratum (e.g. treatment) interactions with covariates and with the baseline hazard function in the proportional hazards (PH) regression model for lifetime data. We consider models incorporating stratum interactions both with and without stratification of the risk sets in the likelihood function, and describe likelihood ratio statistics for tests of the presence of these interactions. We also present step‐down methods for building reduced models which include stratum‐specific parameters corresponding to covariates which interact with treatment. We apply PH models with such interactions to a clinical trial of DES in the treatment of prostate cancer to determine optimal treatment conditional on each patient's covaria

ISSN:0277-6715    

DOI:10.1002/sim.4780050110

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

年代:1986

数据来源: WILEY

摘要:

AbstractWe show that the generalized F family is a useful tool for regression analysis with censored survival data. We discuss maximum likelihood estimation and give asymptotic procedures for calculating confidence intervals, tests of significance for the parameters, life expectancy, quantiles and survival rates. Survival data on 704 ovarian carcinoma patients serve to demonstrate the utility of the model.

ISSN:0277-6715    

DOI:10.1002/sim.4780050111

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.4780050112

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

年代:1986

数据来源: WILEY