ISSN:0277-6715    

DOI:10.1002/sim.4780060102

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

年代:1987

数据来源: WILEY

摘要:

AbstractA multiple choice test with nine statistical questions was sent to a random sample of Danish doctors to assess their knowledge of elementary statistical expressions (SD, SE,p0·05 andr). One hundred and forty eight (59 per cent) of 250 doctors answered the questions. The test was also completed by 97 participants in postgraduate courses in research methods, mainly junior hospital doctors. The median number of correct answers was 2·4 in the random sample and 4·0 in the other sample of doctors. It is concluded that the statistical knowledge of most doctors is so limited that they cannot be expected to draw the right conclusions from those statistical analyses which are found in papers in medical journals. Sixty‐five per cent of the doctors in the random sample stated that it is very important that this problem is r

ISSN:0277-6715    

DOI:10.1002/sim.4780060103

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

年代:1987

数据来源: WILEY

摘要:

AbstractIn evaluating therapies, clinical investigators often need to rely on the published clinical trial literature which may be biased in favour of studies with positive or ‘encouraging’ results and this may lead to erroneous conclusions of therapeutic effectiveness. The problem of publication bias can be magnified when the evaluation is based on a pooled analysis of clinical trial results, since in this case even small differences between treatment groups may reach statistical significance.In this paper a model is developed for pooling the results of clinical trials which is free from publication bias. It is proposed that an international registry of all clinical trials be established with the objectives and endpoints of each trial clearly defined in the register. In this way for each therapeutic issue researchers can select a cohort of clinical trials independently from the trial results.The approach is illustrated using the International Cancer Research Data Bank (ICRDB) registry of cancer clinical trials to evaluate the effect of chemotherapy on survival in advanced ovarian cancer. In this example, the conclusions based on a pooled analysis ofregisteredtrials have important differences from a more traditional review of thepublishedtrials. Implications of the results and problems in implementing the model are discus

ISSN:0277-6715    

DOI:10.1002/sim.4780060104

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

年代:1987

数据来源: WILEY

摘要:

AbstractPrognostic factors often appear as covariates in clinical trials designed to estimate treatment effects. These factors are usually subject to measurement error and lead to decreased efficiency in the estimation of the treatment effect. We use Weibull regression models and asymptotic theory to derive the efficiency of estimation obtained by adjusting for one dichotomous and one continuous covariate measured with error. An application to a clinical trial involving advanced lung cancer patients illustrates the results.

ISSN:0277-6715    

DOI:10.1002/sim.4780060105

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

年代:1987

数据来源: WILEY

摘要:

AbstractThis paper discusses statistical techniques for the analysis of dichotomous data arising from a design in which the investigator randomly assigns each of two clusters of possibly varying size to interventions within strata. The problem addressed is that of assessing the statistical significance of the intervention effect over all strata. We propose a weighted pairedt‐test based on the empirical logistic transform for designs that randomize large aggregate clusters in each of several strat

ISSN:0277-6715    

DOI:10.1002/sim.4780060106

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

年代:1987

数据来源: WILEY

摘要:

AbstractA new sample size formula is derived herein for matched‐pair case‐control studies. This result is based on an unconditional approach to the use of McNemar's statistic. We contrast this method for determining sample size and power with Schlesselman's conditional approach and compare the results numerically in a Monte Carlo st

ISSN:0277-6715    

DOI:10.1002/sim.4780060107

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

年代:1987

数据来源: WILEY

摘要:

AbstractDifferent distributions of confounding variables in populations complicate any comparison of the relative frequency of an event. To resolve this, methods for fitting statistical models to tables of rates have recently been developed. One such model is the multiplicative model. We performed a Monte Carlo study of the multiplicative model for a 4 × 3 table of rates. For small samples the likelihood ratio test statistic was conservative for small expected cell counts, liberal for moderate expected counts, and performed well for large expected counts. The weighted least squares test statistic was generally more conservative and less powerful than both the likelihood ratio statistic and the Pearson statistic

ISSN:0277-6715    

DOI:10.1002/sim.4780060108

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

年代:1987

数据来源: WILEY

摘要:

AbstractWe investigate the frequency in occupational studies of falsely identifying significantly elevated cause‐specific mortality in the presence of multiple comparisons. When one investigates a standard battery of causes of death, use of a standardized mortality ratio as a summary index results in an excessive experimental error rate, but one can control the error rate with use of standard procedures that limit the type I error. When a major disease category for an occupational cohort has a lower rate than expected, then with use of a proportionate mortality ratio as a summary index, the standard procedures for control of the type I error are inadequate. In this situation, use of a proportionate mortality ratio as a summary index is likely to result in the false identification of an excess cause‐specific mortality more often than previously acknowled

ISSN:0277-6715    

DOI:10.1002/sim.4780060109

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

年代:1987

数据来源: WILEY

摘要:

AbstractOne may encounter the application of the two independent samplest‐test to ordinal scaled data (for example, data that assume only the values 0, 1, 2, 3) from small samples. This situation clearly violates the underlying normality assumption for thet‐test and one cannot appeal to large sample theory for validity. In this paper we report the results of an investigation of thet‐test's robustness when applied to data of this form for samples of sizes 5 to 20. Our approach consists of complete enumeration of the sampling distributions and comparison of actual levels of significance with the significance level expected if the data followed a normal distribution. We demonstrate under general conditions the robustness of thet‐test in that the maximum actual level of significance is close to the declare

ISSN:0277-6715    

DOI:10.1002/sim.4780060110

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

年代:1987

数据来源: WILEY

摘要:

AbstractMissing data complicate the analysis of paired categorical data. This paper considers with the use of the EM algorithm, the maximum likelihood estimation and likelihood ratio test for incomplete square tables with missing data. An example involving the susceptibility of micro‐organisms to antimicrobial drugs illustrates the procedur

ISSN:0277-6715    

DOI:10.1002/sim.4780060111

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

年代:1987

数据来源: WILEY