摘要:

AbstractPooling patient data from multi‐institutional medical chart review occurs commonly in the study of cancer and other diseases. To determine the consistency of reporting among institutions, we presented a test set of 25 standardized medical charts to coders at 18 Comprehensive Cancer Centers and compared their resulting codes. This study measures the reproducibility of coding by different persons, but does not assess the accuracy of the underlying medical record. Among 34 data items, we found high disagreement rates in coding stage of disease (14 per cent) and date of diagnosis (8 per cent). Primary site, histologic type and other key items had good reproducibility (disagreement rates<5 per cent). A number of minor disagreements indicated that detailed distinctions could not be reliably coded from medical chart

ISSN:0277-6715    

DOI:10.1002/sim.4780010302

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe San Serriffe Game is a simulated epidemiological research exercise for demonstrating survey methods to medical postgraduates. A computer model has been developed to simulate medical and socio‐economic data relating to births and neonatal deaths on the imaginary island of Lower Caisse, San Serriffe. Participants, working in teams, are asked to investigate the extent and causes of neonatal mortality in Lower Caisse and to make recommendations which will bring about a reduction in the mortality rate. Participants are expected to implement some of the ideas learnt in parallel lecture sessions on the planning, design and analysis of survey wor

ISSN:0277-6715    

DOI:10.1002/sim.4780010303

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

年代:1982

数据来源: WILEY

摘要:

AbstractOf the several types of summary odds ratios in use in epidemiology, only those proposed by Mantel and Haenszel and Miettinen do not assume homogeneity (constancy) of stratum‐specific parameters. Under heterogeneity, Miettinen's estimators consistently estimate meaningful epidemiologic parameters, whereas the asymptotic expectation of the Mantel‐Haenszel odds ratio varies according to irrelevant features of the sampling design. Although one can modify the Mantel‐Haenszel summary to overcome the latter problem, one can also extend the Miettinen estimators to sparse data and thus limit the use of Mantel‐Haenszel summaries to situations in which the homogeneity hypothesis is reasonable. This paper provides formulae for the extended Miettinen estimators and large‐sample variances and confidence limits for summary ratios under hete

ISSN:0277-6715    

DOI:10.1002/sim.4780010304

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

年代:1982

数据来源: WILEY

摘要:

AbstractThis paper extends Levin's measure of attributable risk1to adjust for confounding by aetiologic factors other than the exposure of interest. One can estimate this extended measure from case‐control data provided either (i) from the control data one can estimate exposure prevalence within each stratum of the confounding factor; or (ii) one has additional information available concerning the confounder distribution and the stratum‐specific disease rates. In both cases we give maximum likelihood estimates and their estimated asymptotic variances, and show them to be independent of the sampling design (matched vs. random). Computer simulations investigate the behaviour of these estimates and of three types of confidence intervals when sample size is small relative to the number of confounder strata. The simulations indicate that attributable risk estimates tend to be too low. The bias is not serious except when exposure prevalence is high among controls. In this case the estimates and their standard error estimates are also highly unstable. In general, the asymptotic standard error estimates performed quite well, even in small samples, and even when the true asymptotic standard error was too small. By contrast, the bootstrap estimate2tended to be too large. None of the three confidence intervals proved superior in accuracy to the other two. Thus there appears no advantage in using the log‐based interval suggested by Walter3′4which is always longer than the simpler symmetric i

ISSN:0277-6715    

DOI:10.1002/sim.4780010305

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

年代:1982

数据来源: WILEY

摘要:

AbstractWe develop the application of age, period and cohort models to the representation of tables of age‐ and period‐specific rates. A derivation is given by way of a familiar graphical technique. The identifiability problem is discussed, identification techniques are reviewed and a new approach is recommended that is based upon the success of the three two‐variable submodels. Other constraints are introduced that enhance interpretation. Examples are given for two sites of cancer. This approach is contrasted with other methods designed to demonstrate trends. Finally, standard errors of the parameters and tests of goodness of fit are disc

ISSN:0277-6715    

DOI:10.1002/sim.4780010306

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

年代:1982

数据来源: WILEY

摘要:

AbstractIn designing a clinical trial, the investigator must often decide whether or not to exclude certain patients from randomization. Using Bayesian analysis this paper proposes a criterion for making this decision, based on an extension of Colton's model for the choice between two medical treatments.

ISSN:0277-6715    

DOI:10.1002/sim.4780010307

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

年代:1982

数据来源: WILEY

摘要:

AbstractWe investigate the power of detecting treatment differences by the stratified logrank test for balanced samples as compared to samples with unequal allocation to treatments within strata. Given non‐stratified randomization to treatments, we relate power losses to their probability of occurrence. In addition, we evaluate the likelihood of zero cells. For power calculations, we employ an asymptotic formula and complement by Monte Carlo simulations to verify results in small samples. In the cases investigated, our results show that large power losses due to imbalance are relatively unlikely with 2 strata. Small strata, however, involve a non‐negligible probability of wasting all observations because of zero cells or censor

ISSN:0277-6715    

DOI:10.1002/sim.4780010308

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

年代:1982

数据来源: WILEY

摘要:

AbstractEqual allocation of patients to treatment in a randomized clinical trial may have disadvantages ethically if the new treatment is believed to be at least as beneficial as the standard treatment. Others have considered, in a non‐sequential setting, unbalanced randomized designs which allocate fewer patients to the potentially inferior standard treatment. This paper examines unbalanced randomized designs in a sequential comparison of two exponential survival distributions using the progressively censored Savage test. The results reveal no substantial sacrifice in asymptotic power or early stopping propertie

ISSN:0277-6715    

DOI:10.1002/sim.4780010309

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe advantages and disadvantages of using extraneous information about the relationship between variate and covariate in analysis of covariance are examined. The problem is considered both theoretically and by a simulation study. It is found that the usefulness of extraneous information in increasing the precision of analysis of covariance can be assessed using simple formulae.

ISSN:0277-6715    

DOI:10.1002/sim.4780010310

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

年代:1982

数据来源: WILEY

ISSN:0277-6715    

DOI:10.1002/sim.4780010311

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

年代:1982

数据来源: WILEY