摘要:

AbstractClinical research often rests on statistical interpretation of numerical data. Thus, effective collaboration between clinician and statistician can have central importance. Interaction in the planning phases of a project can identify tractable scientific and statistical problems that will need attention and can help avoid intractable ones. The central need is for clear, broad, specific two‐way communication on scientific issues and research role

ISSN:0277-6715    

DOI:10.1002/sim.4780030102

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

年代:1984

数据来源: WILEY

摘要:

AbstractProportional mortality analyses are traditionally considered to be unreliable because they lack information on persons at risk. Standardized mortality ratios (SMRs) are often used in preference to proportional mortality ratios (PMRs) even when the denominator or numerator of rates is known to be biased. Examination of data from 30 randomly selected occupational units described by the U.K. Office of Population Censuses and Surveys (OPCS) revealed, however, that age‐standardized cause‐specific SMRs and PMRs have an almost constant relationship: the ratio of the cause‐specific SMR to the cause‐specific PMR closely approximating the all‐cause SMR of the group under consideration. Hence, a PMR above 100 almost always indicates that the corresponding cause‐specific SMR is greater than the all‐cause SMR (and vice versa). Furthermore, approximately 70 per cent of conditions with significantly high PMRs above 200 have corresponding SMRs which are also significantly high. When cautiously interpreted, the PMR may, therefore, be a useful indicator of an increased frequency of disease in a particular occupational o

ISSN:0277-6715    

DOI:10.1002/sim.4780030103

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

年代:1984

数据来源: WILEY

摘要:

AbstractWe performed a Monte Carlo computer simulation of the Walker‐Duncan logistic regression technique in a typical epidemiologic prospective setting and analysed the results with respect to the accuracy and reliability of the regression estimates and the associated statistical significance tests (Z‐tests). The results strongly suggest that the estimates were neither accurate nor reliable. The magnitude of the difference between the average estimated regression coefficient and its true population value did not necessarily decrease as the sample size increased. The average estimated standard deviation of the estimate of the regression coefficient either overestimated or underestimated the actual standard deviation, the former occurring most, but not all, of the time. The significance tests (a two‐tailedZ‐test with a significance level of 0.05) had actual type I errors ranging from 0.00 to 0.24 for different samples. This approach is therefore inadequate as an epidemiologic tool for analysis of a Framingham‐type prospective study. Further simulation studies are

ISSN:0277-6715    

DOI:10.1002/sim.4780030104

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

年代:1984

数据来源: WILEY

摘要:

AbstractA narrow case definition can lead to greater in clarity in case‐control studies, but it can also lead to either a gain or a loss in the power of statistical tests. Under plausible assumptions, the loss of power can be in excess of 30 per cent, and the gain can be in excess of 50 per cent. If at least one third of the total study size consists of narrowly defined cases, the loss of power will often be negligible, whereas the gain can be substantia

ISSN:0277-6715    

DOI:10.1002/sim.4780030105

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

年代:1984

数据来源: WILEY

摘要:

AbstractReports of cancer clinical trials often attempt to evaluate whether tumour response is associated with prolonged survival. Proper analysis requires accounting for the time‐dependent nature of response status. We review a valid and relatively simple method of significance testing for this problem, and develop a corresponding non‐parametric method for displaying the association between survival and occurrence of response. The new method applies to many other clinical problems involving representation and the association between survival and the occurrence of an event. We illustrate the method with data from two clinical tri

ISSN:0277-6715    

DOI:10.1002/sim.4780030106

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

年代:1984

数据来源: WILEY

摘要:

AbstractWe present an experimental design for the evaluation of therapeutic preferences among well established similar modes of therapy. The measure of the degree of preference is based on clinical decisions to continue or discontinue the current treatment at each patient visit. Such a trial simulates decision‐making in ordinary clinical practice, while adhering to the scientific principles of experimental design, and it alleviates some of the ethical problems inherent in randomized allocation of a treatment for a period of fixed length in conventional controlled trials. We discuss the design and methods of analysis and illustrate their application with data from a trial comparing three alternative drug treatments for chronic asthma.Such clinical trials provide a mechanism for examining concordance between the relative efficacy of treatments predicted from conventional controlled clinical trials and their ultimate performance in ordinary clinical practice, expressed in terms of therapeutic preference

ISSN:0277-6715    

DOI:10.1002/sim.4780030107

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

年代:1984

数据来源: WILEY

摘要:

AbstractThis presentation attempts to clarify certain caveats that apply to the use of linkage analysis when the genetics of one of the characters is not completely known. The effects of linkage and association can be difficult to distinguish both within pedigrees and across the general population. Linkage analysis methods are not robust to departures from the assumptions of the model. These assumptions do not allow for the possibility that association may be present which is due to both genetic systems having an effect on one of the phenotypes. Analysis directed towards detecting the presence of such association may be affected by stratification when unrelated individuals are analysed and is confounded by linkage if this is present when related individuals are analysed. Testing for and estimating linkage simultaneously with association using whole pedigree data is advocated and an outline of the required approach is given.

ISSN:0277-6715    

DOI:10.1002/sim.4780030108

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

年代:1984

数据来源: WILEY

摘要:

AbstractWe investigated interobserver variation between three physician readers in the independent classification of chest radiographs from 1771 taconite workers for pneumoconiosis. We analysed variation with a general methodology for the analysis of categorical data, and quantified interobserver agreement in terms of kappatype statistics. The results revealed considerable variation in the profusion of opacities reported by each observer. This was especially so for the earliest radiographic changes, but variation also occurred with the small number of films in the series showing category 2 pneumoconiosis or over. Variation in the classification of profusion of small opacities was greater in films of poor quality, and also increased with the length of time between taking and reading the film (film age). We could not account for the effect of film age by controlling for film quality, as subjectively assessed by the readers.

ISSN:0277-6715    

DOI:10.1002/sim.4780030109

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

年代:1984

数据来源: WILEY

摘要:

AbstractThe problem of when to include a covariate in the analysis of variance is considered in the special case of organ weight analysis in animal toxicology studies. The covariate is bodyweight prior to death, which may be subject to treatment effects. A simulation study is carried out to compare four rules for deciding whether or not to include the covariate. It is concluded that if there is background information which shows a linear relationship between variate and covariate it is advisable to adjust for the covariate, however weak the relationship may appear to be on the current set of data. Alternative procedures lead to unacceptably high Type I error rates.

ISSN:0277-6715    

DOI:10.1002/sim.4780030110

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

年代:1984

数据来源: WILEY

ISSN:0277-6715    

DOI:10.1002/sim.4780030111

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

年代:1984

数据来源: WILEY