摘要:

AbstractOver the last decade, considerable interest has focused on sample size estimation in the design of clinical trials. The resulting literature is scattered over many textbooks and journals. This paper presents these methods in a single review and comments on their application in practice.

ISSN:0277-6715    

DOI:10.1002/sim.4780030302

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

年代:1984

数据来源: WILEY

摘要:

AbstractEmploying randomization theory, this note examines the manner in which a clinical trial employing Zelen's randomized consent design yields an estimated treatment effect free of selection bias. We also examine the concept of ‘treatment dilution’ in this des

ISSN:0277-6715    

DOI:10.1002/sim.4780030303

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

年代:1984

数据来源: WILEY

摘要:

AbstractThe allocation of treatment to patients in a clinical trial while balancing for prognostic factors is usually done by a co‐ordinating centre when all the factors are known. In a trial comparing two treatments of acute rejection of renal allografts some prognostic factors become available to the physician only at the moment of the diagnosis of the rejection. This diagnosis is often made out of office hours, whereas immediate start of treatment is essential. It is shown here that the co‐ordinating centre is still able to control the allocation of patients to treatment groups if a small number of prognostic factors is known only to the physic

ISSN:0277-6715    

DOI:10.1002/sim.4780030304

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

年代:1984

数据来源: WILEY

摘要:

AbstractClinical trials of treatments for rare or fatal diseases must often use historical rather than randomized concurrent controls. Randomized trials may not be possible if (1) the number of patients available is quite small, (2) ethical considerations discourage the assignment of patients to control treatments known to be ineffective or (3) some evidence suggests that the proposed new treatment is substantially more effective than the control. We suggest that, when randomization is not feasible, adequately maintained medical registers can serve as a source of control patients. Investigators must pay careful attention to prognostic factors that might bias the results. However, statistical techniques for controlling such bias exist and, if these are properly employed, registry‐derived historical controls can be used to evaluate the effectiveness of treatmen

ISSN:0277-6715    

DOI:10.1002/sim.4780030305

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

年代:1984

数据来源: WILEY

摘要:

AbstractIn a multi‐hospital surveillance system for detecting increases in congenial malformation rates, the performance of the set technique applied individually to hospitals and of the cumulative sum (Cusum) technique applied to the aggregate of hospitals has been compared using a Monte Carlo method. The Cusum technique appears to be both more sensitive to real increases and less likely to issue false alarm

ISSN:0277-6715    

DOI:10.1002/sim.4780030306

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

年代:1984

数据来源: WILEY

摘要:

AbstractThis paper illustrates the use of latent class analysis to classify 50,000 infants into a small number of classes or case types, as a preliminary to a study of the allocation of neonatal hospital resources throughout Scotland. Information, extracted from a detailed neonatal discharge record, was summarized by 11 clinical and diagnostic catagorical variables. Statistical models incorporating 1 to 6 latent classes were then estimated using the EM algorithm. The 4 class model was chosen because it provided a good description of the data and the resulting classes had a medical interpretation. The factors influencing the choice of model are discussed and goodness of fit tests are presented. The stability of the classes was also investigated using random halves of the data and an earlier comparable data set.

ISSN:0277-6715    

DOI:10.1002/sim.4780030307

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

年代:1984

数据来源: WILEY

摘要:

AbstractThis paper describes a distribution‐free method for the automatic classification of individuals by phenotype of the serum protein α1‐antitrypsin. This method achieved 74 per cent agreement and a Kappa value of 0.24 when compared to the conventional classification procedure on an independent testing sample. The methodology is appropriate for many classification problems, particularly when the true classes and the reliability of the conventional procedure are unk

ISSN:0277-6715    

DOI:10.1002/sim.4780030308

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

年代:1984

数据来源: WILEY

摘要:

AbstractWe study three approaches for the analysis of ordinal pain data. The first is essentially non‐parametric, based on partitioning the goodness‐of‐fit statistic for testing the homogeneity model. The other two involve the modelling of quite different logit functions of the multinomial probabilities. We discuss and compare the characteristics of these three approaches using actual data from an analgesic

ISSN:0277-6715    

DOI:10.1002/sim.4780030309

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

年代:1984

数据来源: WILEY

摘要:

AbstractMethods for estimating the size of a closed population often consist of fitting some model (e.g. a log‐linear model) to data with a missing cell corresponding to the members of the population missed by all reporting sources. Although the use of the asymptotic standard error is the usual method for forming confidence intervals for the population total, the sample sizes are not always large enough to produce valid confidence intervals. We propose a method for forming confidence intervals based upon changes in a goodness‐of‐fit statistic associated with changes in trial values of the population

ISSN:0277-6715    

DOI:10.1002/sim.4780030310

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

年代:1984

数据来源: WILEY

摘要:

AbstractWe provide a brief summary of the theory of ridge regression, regress reported rates of congenital syphilis on three stages of adult syphilis using both ridge regression and least squares techniques, and discuss the results. We also develop a principal components regression model for the same example and compare the results.The example demonstrates the usefulness of ridge regression to handle multicollinearity in data. Problems of overestimation and instability associated with ordinary least squares estimates of these non‐orthogonal data diminish with use of the ridge regression technique

ISSN:0277-6715    

DOI:10.1002/sim.4780030311

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

年代:1984

数据来源: WILEY