摘要:

AbstractAnalyses of spontaneous abortion rates often include special provisions to account for the presumed distorting effects that arise because of the presence of habitual aborters. In this paper, I establish a framework for investigating the effects of the presence in study groups of such women. I then examine the strengths and weaknesses of some of the analysis strategies in current use, both in situations where the study group is homogeneous and where there are high‐risk women present. I show that the concept of habitual aborter is not useful and can be misleading, and I suggest that one take a broader view of heterogeneit

ISSN:0277-6715    

DOI:10.1002/sim.4780050602

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

年代:1986

数据来源: WILEY

摘要:

AbstractThis paper presents an ‘optimal’ procedure for the use of the ‘sets’ method, a system proposed for surveillance of congenital malformations.1Comparisons over a number of examples shows that the given procedure represents a clear improvement over the one originally proposed, and, in some conditions, is more efficient than the cusum

ISSN:0277-6715    

DOI:10.1002/sim.4780050603

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

年代:1986

数据来源: WILEY

摘要:

AbstractWe present a method for estimating incidence from age‐specific prevalence data for an irreversible disease where the mortality risks may differ for persons with and without the disease. This method is an extension of previously presented methodology1for estimating incidence from prevalence for a disease that does not entail differential mortality. An application to senile cataract illustrates the metho

ISSN:0277-6715    

DOI:10.1002/sim.4780050604

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe recent growth of occupational epidemiology has led to a resurgence of interest in the hybrid epidemiologic study design of Kupper et al.,1which has come to be termed a ‘case‐base’ or ‘case‐cohort’ design. This paper shows how the adjustment method for the risk ratio estimate given by Kupper et al. may have substantial bias, and also shows how one must modify conventional adjustment techniques (such as the Miettinen, Woolf and Mantel ‐Haenszel methods) when used with hybrid designs. This paper also provides the necessary modifications for tests and confide

ISSN:0277-6715    

DOI:10.1002/sim.4780050605

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe relation between sensitivity, specificity and prevalence is illustrated by means of a graphical device, applied to two diagnostic questions on gastroenteritis in children. The relation between the predictive values and the prevalence is also illustrated graphically.

ISSN:0277-6715    

DOI:10.1002/sim.4780050606

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

年代:1986

数据来源: WILEY

摘要:

AbstractTime‐series techniques are applied to an analysis of the use of neurodiagnostic procedures in Athens, to evaluate the effect of the introduction of computer tomography. Results confirm the usefulness of such techniques, but illustrate the dependence of their successful application on the nature and quality of dat

ISSN:0277-6715    

DOI:10.1002/sim.4780050607

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe effects of a number of controllable factors on the response rate of mothers to a postal questionnaire were assessed by a series of experiments. In one a factorial design was used to look at seven factors with a random sample of 1600 mothers. The main findings were that the responses to questionnaires of 8,16 or 24 pages were similar, but that rather more mothers replied when the questionnaires contained only factual questions than when they covered both facts and attitudes. Another experiment, based on a similar sample, compared the response rates when the questionnaires were sent out by a government organization or by the Institute for Social Studies in Medical Care, and found no difference. The final experiment looked at the effect of precoding the answers or asking respondents to tick boxes beside their replies and again found no difference in response rates. The overall response rate was 79 per cent, but this varied between 66 and 87 per cent in the ten randomly selected study areas‐a much greater variation than that found with any of the experimental factor

ISSN:0277-6715    

DOI:10.1002/sim.4780050608

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

年代:1986

数据来源: WILEY

摘要:

AbstractWe propose a class of models for the joint cumulative distribution function (c.d.f.) of the values of two independent readings of percentage stenosis from a coronary arteriography. We show that these models are identifiable and that a certain subclass has unique consistent estimators for the parameters in question. We obtain these estimates for a data set from a substudy of the Coronary Artery Surgery Study (CASS).

ISSN:0277-6715    

DOI:10.1002/sim.4780050609

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe two tailed Fisher's exact P value is extremely sensitive to small perturbations in 2 × 2 contingency tables. An example indicates that a 1 per cent increase in the denominator of one treatment group results in a 32 per cent drop in the exact P value, but a mere 0.1 per cent decrease in the treatment success rate. This is equivalent to the increase in significance obtained by a 20 per cent increase in the sample size of both treatments without changing the observed success rates. This drop results from small changes in the probabilities of unobserved events. A systematic evaluation of 920 pairs of similar contingency tables shows that these fluctuations occur frequently over a wide range of sample sizes and significance levels. Doubling the one tailed exact P value provides a more consistent measure of inferential strength. We discuss various chi‐squared continuity correctio

ISSN:0277-6715    

DOI:10.1002/sim.4780050610

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

年代:1986

数据来源: WILEY

摘要:

AbstractWe investigate factors associated with the survival of end‐stage renal disease patients on hemodialysis. A model derived for non‐diabetics includes five significant prognostic factors: age at initiation of dialysis, arteriosclerotic heart disease, cerebrovascular accident, cancer and chronic obstructive pulmonary disease. For diabetics, age at initiation of dialysis was the only significant prognostic factor.We also show that (i) a simple exponential model adequately represents hemodialysis survival data, (ii) the relationship between age and survival hazard is not log‐linear and (iii) data for diabetics require independent analysis or inclusion of interaction terms. In this paper, we chose the first app

ISSN:0277-6715    

DOI:10.1002/sim.4780050611

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

年代:1986

数据来源: WILEY