摘要:

AbstractGenetic epidemiology is the analysis of the familial distributions of traits, with a view to understanding any possible genetic basis; the fundamentals of this area are reviewed. The terminology of genetic models is fully described, since it is this wealth of terminology which can make it difficult for a statistician to enter the area. The statistical approaches to the analysis of data on sets of interrelated individuals are then discussed, and resulting problems of sampling design and analysis are considered.

ISSN:0277-6715    

DOI:10.1002/sim.4780050402

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

年代:1986

数据来源: WILEY

摘要:

AbstractAn approach to the problem of a single study lacking adequate power to examine an important question is to combine the data from several studies to allow a more powerful test of the hypothesis in question. The present paper describes a method used by the International Collaborative Group to pool data on 54,492 men aged 40–69 from 10 population studies in 7 countries to examine the association between cholesterol level and risk of death from cancer. Furthermore, there was a suggestion that the inverse association observed in some studies might be the result of an effect of undetected cancer on cholesterol level, rather than an increase in cancer risk resulting from low cholesterol levels. This paper describes the process for selection of the method used to evaluate this possibility over other potential approaches and the results obtained in the analysis of the International Collaborative Group data that support this hypothesis. This report also indicates how one might expect some of the analyses described to compare with analyses based on a discrete version of the Cox proportional hazards mode

ISSN:0277-6715    

DOI:10.1002/sim.4780050403

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

年代:1986

数据来源: WILEY

摘要:

AbstractFour unequal allocation designs for cohort and case‐control studies that incorporate cost and power are considered and compared with the equal allocation design, with the aim of providing researchers some flexibility in planning their studies. It is found that the type of design to be adopted depends on available resources and projected needs. In the case of tight expenditure, the minimized cost design is the optimal, whereas the maximized power design may be sought if the researcher intends to ensure a high chance of detecting any clinically significant relative risk of diseas

ISSN:0277-6715    

DOI:10.1002/sim.4780050404

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe widely used ‘person‐years method’ of calculating expected mortality has been discussed recently by several authors. In studies where mortality is either lower or higher than the standard mortality of some reference population, the use of exposure to death as an estimator of the expected number of deaths will generally lead to bias, always exaggerating the difference between study and standard mortality. This bias is examined in a proportional hazards model. The recent suggestion by Hartzet al.1of calculating the mortalities of individuals during their ‘potential follow‐up time’ is claimed to be only rarely feasible

ISSN:0277-6715    

DOI:10.1002/sim.4780050405

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

年代:1986

数据来源: WILEY

摘要:

AbstractThis paper proposes a new procedure for estimating normal ranges of clinical laboratory tests, which can be applied to data with possibly more than one outlier from healthy subjects. The proposed procedure determines the optimal model among a class of models in which it is assumed that (1) an observed distribution of ‘normal values’ can be transformed to the Gaussian form by one of several specified transformations, and (2) if there exist outliers among the data, then each of the transformed outliers also follows a Gaussian distribution with different mean from, but the same variance as, the transformed distribution of normal values. The optimal model is defined as the best combination of the transformation to normality and the number of outliers identified, and is selected by the Akaike information criterion (AIC). Our procedure is illustrated with data from 200 healthy male subjects on 25 laboratory te

ISSN:0277-6715    

DOI:10.1002/sim.4780050406

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

年代:1986

数据来源: WILEY

摘要:

AbstractA calibration line is used to define the relationship between a new clinical technique and a standardin vitrolaboratory methodology. Discrimination intervals quantify the reliability of inverse estimates obtained from the calibration line. Applied to transcutaneousP CO 2monitoring, a newin vivomeasurement, discrimination intervals for inverse estimates of arterialP CO 2range in size from 10 to 50 torr (1.33–6.67 kPa), or more, depending on the values of statistical parameters selected. Discrimination interval analysis shows that the inverse estimates are more reliable near the means. Also, it indicates that the primary value of transcutaneousP CO 2monitoring lies not in providing accurate inverse estimates of arterialP CO 2, but instead, in monitoring short‐t

ISSN:0277-6715    

DOI:10.1002/sim.4780050407

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

年代:1986

数据来源: WILEY

摘要:

AbstractIn the first seven cases of transfusion‐associated acquired immunodeficiency syndrome (TA‐AIDS) with completion of blood donor investigations, there was identification of at least one person (a high‐risk donor‐ HRD) in each donor set who might have transmitted the disease. Using three definitions of an HRD, we estimated the prevalence of HRDs in the overall donor population and used the binomial distribution to calculate the probabilities of finding at least the observed numbers of donor sets with one or more HRDs. These probabilities‐0.028, 0.007 and 0.014, respectively‐allowed us to reject the null hypothesis that the number of cases of TA‐AIDS exposed to an HRD was not greater than that expected by chance, based on the total number of donors to which each case was exposed and the estimated proportion of HRDs in the overall donor population. We concluded that there was a statistically significant association between HRD

ISSN:0277-6715    

DOI:10.1002/sim.4780050408

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

年代:1986

数据来源: WILEY

摘要:

AbstractAn approach is described for estimating the dose of a new drug which is equipotent to an established dose of an old drug. The approach is basically that of the parallel‐line assay but it can allow for concomitant variables and, by exploiting the facilities available in the statistical computer package GLIM (generalized linear interactive modelling), the approach can be applied when the residuals conform to one of a number of distributions and, with suitable safeguards, to continuous, discrete and even ‘scored’ responses. In some circumstances, it is necessary to obtain confidence limits by Efron's ‘bootstrap’ technique. The method is illustrated with results from a trial of two premedicant drugs in

ISSN:0277-6715    

DOI:10.1002/sim.4780050409

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

年代:1986

数据来源: WILEY

摘要:

AbstractThree recent sequential methods, group sequential analysis (GSA), the sequential probability ratio test (SPRT) and the triangular test (TT) are well suited to randomized clinical trials with a censored response criterion, as they do not require matched pairs of patients.We undertook a simulation study to investigate their statistical properties and to compare these three methods with the fixed‐sample design. Our results suggest that (i) the three methods have the expected statistical properties for size and power; (ii) they allow an important reduction of the average number of events before stopping, except with GSA when there is no treatment difference; (iii) the triangular test (closed design) appears the optimal design, as the variance of the number of events is smaller than with the sequential probability ratio test (open design) and (iv) analysis after every twenty new events does not alter the statistical properties of these sequential methods and enhances their usefulnes

ISSN:0277-6715    

DOI:10.1002/sim.4780050410

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

年代:1986

数据来源: WILEY

摘要:

AbstractWe consider a fixed‐sample parallel‐group clinical trial with an interim analysis that testsHo: μx= μyagainstH1: μxμyand the power at the final analysis are not appreciably affected by performing the interim analysis for certain relevant critica

ISSN:0277-6715    

DOI:10.1002/sim.4780050411

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

年代:1986

数据来源: WILEY