摘要:

AbstractNeural networks are considered by many to be very promising tools for classification and prediction. The flexibility of the neural network models often result in over‐fit. Shrinking the parameters using a penalized likelihood is often used in order to overcome such over‐fit. In this paper we extend the approach proposed by FARAGGI and SIMON (1995a) to modeling censored survival data using the input‐output relationship associated with a single hidden layer feed‐forward neural network. Instead of estimating the neural network parameters using the method of maximum likelihood, we place normal prior distributions on the parameters and make inferences based on derived posterior distributions of the parameters. This Bayesian formulation will result in shrinking the parameters of the neural network model and will reduce the over‐fit compared with the maximum likelihood estimators. We illustrate our proposed method on a simulated and a rea

ISSN:0323-3847    

DOI:10.1002/bimj.4710390502

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe commonly used method to test for the binomial distribution is thex2‐test. In this paper, we introduce an alternative method to test for the binomial distribution. SupposeNis the number of sample groups withnindividuals each,xijis thejth sample inith group, a Bernoulli variable with parameter and VVI=s2/[m(1 ‐m)/n]. Then it is well know that the asymptotic distribution of the statistic (N‐ 1) VVI isx2(N‐ 1) under the hypothesisp1= p2= … = pN.Here we find that VVI has an asymptotic normal distributionN(1, 2(1 ‐ 1/n)/(N‐ 1)). Unlike thex2‐statistic, the variance of the normal test statistic is a function ofn.This method is convenient in detecting spatial patterns and dispersion in the study of diseased organisms (e.g., plants) i

ISSN:0323-3847    

DOI:10.1002/bimj.4710390503

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThis paper discusses interval estimation for the ratio of the mean failure times on the basis of paired exponential observations. This paper considers five interval estimators: the confidence interval using an idea similar to Fieller's theorem (CIFT), the confidence interval using an exact parametric test (CIEP), the confidence interval using the marginal likelihood ratio test (CILR), the confidence interval assuming no matching effect (CINM), and the confidence interval using a locally most powerful test (CIMP). To evaluate and compare the performance of these five interval estimators, this paper applies Monte Carlo simulation. This paper notes that with respect to the coverage probability, use of the CIFT, CILR, or CIMP, although which are all derived based on large sample theory, can perform well even when the number of pairsnis as small as 10. As compared with use of the CILR, this paper finds that use of the CIEP with equal tail probabilities is likely to lose efficiency. However, this loss can be reduced by using the optimal tail probabilities to minimize the average length whennis small (<20). This paper further notes that use of the CIMP is preferable to the CIEP in a variety of situations considered here. In fact, the average length of the CIMP with use of the optimal tail probabilities can even be shorter than that of the CILR. When the intraclass correlation between failure times within pairs is 0 (i.e., the failure times within the same pair are independent), the CINM, which is derived for two independent samples, is certainly the best one among the five interval estimators considered here. When there is an intraclass correlation but which is small (<0.10), the CIFT is recommended for obtaining a relatively short interval estimate without sacrificing the loss of the coverage probability. When the intraclass correlation is moderate or large, either the CILR or the CIMP with the optimal tail probabilities is preferable to the others. This paper also notes that if the intraclass correlation between failure times within pairs is large, use of the CINM can be misleading, especially when the number of pairs is large.

ISSN:0323-3847    

DOI:10.1002/bimj.4710390504

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThis paper proposes a procedure for testing and classifying data with multiple factors. A two‐way analysis of covariance is used to classify the differences among the batches as well as another factor such as package type and/or product strength. In the test procedure, slopes and intercepts of the main effects are tested using a combination of simultaneous and sequentialF‐tests. Based on the test procedure results, the data are classified into one of four different groups. For each group, shelf life can be calculated accordingly. We examine if the procedure produces satisfactory control of the probability of a Type I error and the power of detecting the difference of degradation rates and intercepts for different nominal levels. The method is evaluated with a Monte Carlo simulation study. The proposed procedure is compared with the current FDA procedure using real d

ISSN:0323-3847    

DOI:10.1002/bimj.4710390505

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractFollowing the linear approach by Stoller a circular discriminant analytical method is described. Marginally, following Ling, a simple method is mentioned to find clusters on a circle. Both methods are distribution‐free and invariant under rotatio

ISSN:0323-3847    

DOI:10.1002/bimj.4710390506

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractA method is developed that caters for the application of correspondence analysis to two‐way contingency tables with one and two ordered sets of categories. The method involves calculating orthogonal polynomials of the type described by EMERSON (1968), and partitioning the chi‐square statistic using the method described in LANCASTER (1953). The method has all the features of simple correspondence analysis, although allows for additional information about the structure and association of the data to be made by isolating location, dispersion and higher order components of the rows and colu

ISSN:0323-3847    

DOI:10.1002/bimj.4710390507

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractA model is presented that allows for the interpretation of the time course of the level of radiolabeled platelets in terms of platelet survival times, rate constant for removal from circulation, pooling time in an extra pool, the rate at which platelets re‐enter circulation from the extra‐pool, and the size of the plasma pool and extra‐pools. The tenets of the model are that: (1) platelets leave the circulation at a rate proportional to their number per unit volume; (2) of the leaving platelets, a fractionbgoes into a pool from which they return into circulation after a pooling time and another fraction (1 ‐b) is irreversibly destroyed; (3) the platelets in the extra‐pool do not “queue up”, and thus the distribution function describing the probability of return is exponential; and (4) the time activity curve of the radiolabeled platelets can be described by the sum of two exponentials. Under steady state conditions, curve fitting allows determination of the constants determining the time activity curve (the respective amplitudes and rate constants of the two exponentials); mean pooling time; relative pool size; and survival time of platelets. The model is applied to data collected from patients over a period from 10 days following reinjection of autologous radiolabe

ISSN:0323-3847    

DOI:10.1002/bimj.4710390508

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractGiven a cone around a curve β in IR3it is shown that there is no relation between the curvature of β and the volume of the cone but, in contrast to the volume, the surface area of the cone depends, albeit rather weakly, on the curvature of β. The geometric meaning of the stereological formulae when applied to cones is considered and it is noted that stereological methods to estimate the surface area of a cone need to be extremely precise to provide information concerning curvature or tortuosi

ISSN:0323-3847    

DOI:10.1002/bimj.4710390509

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

ISSN:0323-3847    

DOI:10.1002/bimj.4710390510

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

ISSN:0323-3847    

DOI:10.1002/bimj.4710390511

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY