摘要:

Between 1982 and 1988 a growth study was carried out at the Division of Pediatric Oncology of the University Hospital of Groningen. A special feature of the project was that sample sizes are small and that ages at entry may be very different. In addition the intended design was not fully complied with. This paper highlights some aspects of the statistical analysis which is based on (1) reference scores, (2) statistical procedures allowing for an irregular pattern of measurement times caused by missing data and shifted measurement times.

ISSN:0039-0402    

DOI:10.1111/j.1467-9574.1993.tb01409.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

A sequence of logistic models is fitted to data from a Dutch follow‐up study on preterm infants (POPS). To examine the adequacy of the model, a recently developed non parametric method to check goodness of fit is applied (le Cessie and Van Houwelingen (1991)). This method uses a test statistic based upon kernel regression methods.In this paper the problem of choosing a “best” bandwidth, corresponding to the greatest power of the test statistic, is avoided by computing the test statistic for a range of different bandwidths. Testing is then based upon the asymptotic distribution of the maximum of the test statistics.The testing method is used as a goodness of fit criterion, and the contribution of each individual observation to the test statistic is used as a diagnostic tool to localize deviations of the model, and to determine directions in which the model can be imp

ISSN:0039-0402    

DOI:10.1111/j.1467-9574.1993.tb01410.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Iterated weighted least squares (IWLS) is investigated for estimating the regression coefficients in a linear model with symmetrically distributed errors. The variances of the errors are not specified; it is not assumed that they are unknown functions of the explanatory variables nor that they are given in some parametric way.IWLS is carried out in a random number of steps, of which the first one is OLS. In each step the error variance at time t is estimated withaweighted sum ofmsquared residuals in the neighbourhood oftand the coefficients are estimated using WLS. Furthermore an estimate of the co‐variance matrix is obtained. If this estimate is minimal in some way the iteration process is stopped.Asymptotic properties of IWLS are derived for increasing sample sizen. Some particular cases show that the asymptotic efficiency can be increased by allowing more than two steps. Even asymptotic efficiency with respect to WLS with the true error variances can be obtained ifmis not fixed but tends to infinity withnand if the heteroskedasticity is smoot

ISSN:0039-0402    

DOI:10.1111/j.1467-9574.1993.tb01411.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

A Bayesian procedure is proposed for the estimation of the weights of the alternatives in a multi‐criteria decision model with data that stem from pair‐wise comparison of alternatives. The prior information restricts the weights to the unit simplex. The posterior results are computed by Monte Carlo integration procedures based on importance sampling. The Bayesian procedure is applied to a case study concerning the choice of a professor of Operations Research (OR). Results are: (1) according to the Bayesian procedure a different candidate would be chosen as professor of OR than according to the maximum likelihood procedure; (2) given the prior and data information, there exists a substantial probability of taking the wrong decision; (3) there exists a ranking of the candidates with a posterior probability greater than one h

ISSN:0039-0402    

DOI:10.1111/j.1467-9574.1993.tb01412.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

ISSN:0039-0402    

DOI:10.1111/j.1467-9574.1993.tb01413.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY