摘要:

AbstractDiagnostic tests are traditionally characterized by simple measures of efficacy such as the sensitivity and the specificity. These measures, though widely recognized and easy to understand, are subject to definitional arbitrariness. Moreover, studies constructed to estimate the sensitivity and specificity are susceptible to a variety of biases. In this paper the various potential problems are described with reference to examples from the diagnostic literature. These difficulties have implications for the design of diagnostic test evaluations, and the choice of suitable measures of test efficacy.

ISSN:0277-6715    

DOI:10.1002/sim.4780060402

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

年代:1987

数据来源: WILEY

摘要:

AbstractThis survey introduces the subject of internal quality assessment from a historical point of view, presents a unified approach to notation, concepts and definitions, and describes briefly those quality control procedures that are used most commonly in clinical chemistry. It is not the aim of this report to comment on all the individual contributions made in this field, but rather to concentrate on the principles. Particular emphasis is centred around assessment criteria to compare the efficiencies of selected control procedures for monitoring analyte concentrations in biological fluids. The question of whether to compare control schemes by means of average run lengths, run length distribution functions or average cost functions is considered. A rationalized approach based on the comparison of optimal procedures, using average run length, is adopted.

ISSN:0277-6715    

DOI:10.1002/sim.4780060403

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

年代:1987

数据来源: WILEY

摘要:

AbstractThis paper provides exact power contours to guide the planning of reliability studies, where the parameter of interest is the coefficient of intraclass correlation p derived from a one‐way analysis of variance model. The contours display the required numbers of subjects k and number of repeated measurements n that provide 80 per cent power for testing Ho:ρ ⩽ ρoversus H1: ρ>ρoat the 5 per cent level of significance for selected values of po. We discuss the design considerations of these

ISSN:0277-6715    

DOI:10.1002/sim.4780060404

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

年代:1987

数据来源: WILEY

摘要:

AbstractA main concern of descriptive epidemiologists is the presentation and interpretation of temporal variations in cancer rates. In its simplest form, this problem is that of the analysis of a set of rates arranged in a two‐way table by age group and calendar period. We review the modern approach to the analysis of such data which justifies traditional methods of age standardization in terms of the multiplicative risk model. We discuss the use of this model when the temporal variations are due to purely secular (period) influences and when they are attributable to generational (cohort) influences. Finally we demonstrate the serious difficulties which attend the interpretation of regular trends. The methods described are illustrated by examples for incidence rates of bladder cancer in Birmingham, U.K., mortality from bladder cancer in Italy, and mortality from lung cancer in Belgiu

ISSN:0277-6715    

DOI:10.1002/sim.4780060405

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

年代:1987

数据来源: WILEY

摘要:

AbstractOur first paper reviewed methods for modelling variation in cancer incidence and mortality rates in terms of either period effects or cohort effects in the general multiplicative risk model. There we drew attention to the difficulty of attributing regular trends to either period or cohort influences. In this paper we turn to the more realistic problem in which neither period nor cohort effects alone lead to an adequate description of the data. We describe the age‐period‐cohort model and show how its ambiguities surrounding regular trends ‘intensify’. We recommend methods for presenting the results of analyses based upon this model which minimize the serious risk of misleading implications and critically review previous suggestions. The discussion is illustrated by an analysis of breast cancer mortality in Japan with special reference to the phenomenon of ‘Clemmese

ISSN:0277-6715    

DOI:10.1002/sim.4780060406

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

年代:1987

数据来源: WILEY

摘要:

AbstractThis paper reports the results of simulations that compare the power of the logrank and generalized Wilcoxon tests in situations where the cure rate model is appropriate.

ISSN:0277-6715    

DOI:10.1002/sim.4780060407

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

年代:1987

数据来源: WILEY

摘要:

AbstractDependence between observations on a dichotomous variable renders invalid the usual chi‐square tests of independence and inflates the variances of parameter estimates. Such a situation occurs, for example, when subjects consist of members of the same family or with repeated observations on the same person. In this paper we describe methods of measuring the extent of correlation (or clustering). We also develop methods of adjusting the Mantel–Haenszel chi‐square test statistic and the variance of the Mantel–Haenszel estimate of a common odds ratio in sets of 2 × 2 contingenc

ISSN:0277-6715    

DOI:10.1002/sim.4780060408

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

年代:1987

数据来源: WILEY

摘要:

AbstractIn 3284 middle‐aged Rotterdam men, the dependency of 9‐year survival on a number of cardiovascular risk factors is analysed. The purpose of this analysis is twofold. First, there is interest in the relationship between total mortality and the continuous variables blood pressure and plasma cholesterol. In accordance with other studies, the results provide further evidence for a U‐shaped relationship. The second purpose is to compare three models theoretically as well as empirically: a piecewise exponential distribution of survival time, Cox's proportional hazards model (both with a log‐linear dependency specification of the mortality rate), and a logistic model. The disadvantage of a logistic model is that it is theoretically not appropriate in longitudinal (prospective) epidemiologic studies. The theoretical advantage of the piecewise exponential distribution to Cox's model is that longitudinal (time) effects on the mortality rate can be specified and estimated directly. Empirically, with 342 deaths all three methods yield quite similar estimates and therefore are almost equally capable of detecting relationships between mortality and the risk factors in the data set

ISSN:0277-6715    

DOI:10.1002/sim.4780060409

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe efficiency of each of two methods for monitoring the occurrence of a rare event, the cusum, carried outmonthly, and the sets techniques, was assessed by use of simulated datasets. The monthly cusum parameters used in this study were those recommended for monitoring of birth defects in a monthly analysis. The sets technique parameters, recommended for monitoring of low‐level epidemics, were adjusted to match the average interval between false alarms to the corresponding values observed for the monthly cusum technique. The results indicate that the relative efficiency of the two techniques depends on the baseline frequency of diagnoses. The sets technique is shown to be more efficient than monthly cusum when the number of cases expected in a year is no greater than five, but less efficient otherwise. In the former case, lengthening the interval between cusum analyses can make the cusum technique more efficient than the sets technique. This possibility deserves further exploration and could affect future recommendation

ISSN:0277-6715    

DOI:10.1002/sim.4780060410

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

年代:1987

数据来源: WILEY

ISSN:0277-6715    

DOI:10.1002/sim.4780060411

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

年代:1987

数据来源: WILEY