ISSN:0162-1459    

DOI:10.1080/01621459.1992.10475204

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Collections of occurrence times of events taking place irregularly in time provide a fairly common, but not broadly discussed, data type. This article is concerned with the particular circumstance of firing times in nerve cells that interact and form networks. The article reviews a progression of statistical analysis techniques: description, association as measured by moments and correlation, regression, and finally likelihood. The data is point process, but may be seen as that of regression and of multivariate analysis in standard parlance. A simple description of data collected simultaneously for one or more cells is provided.

ISSN:0162-1459    

DOI:10.1080/01621459.1992.10475205

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Growth models for tumors commonly are developed for a one-dimensional summary (e.g., number of cells, volume). At the supracellular level, however, ignoring tumor shape leads to oversimplification of the growth mechanism. For example, an oncologist would view the discovery of a compact tumor of volumevdifferently from the discovery of two osculatory compact tumors each of volumev/2. This article presents a growth model that uses shape information at a previous time to describe the tumor at the present time. An analysis is given of three successive two-dimensional images of cell islands, which are obtained from in vitro growth of human breast cancer cells.

ISSN:0162-1459    

DOI:10.1080/01621459.1992.10475206

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Accelerated failure-time regression models with an additional regression model for the surviving fraction are proposed for the analysis of events that may never occur, regardless of censoring, for some people in the population risk set. The models attempt to estimate simultaneously the effects of covariates on the acceleration/deceleration of the timing of a given event and the surviving fraction; that is, the proportion of the population for which the event never occurs. The extended family of the generalized Gamma distribution is used for the accelerated failure-time regression model; the logistic function is used for the regression model of the surviving fraction. The models are applied to the data of interfirm job mobility in Japan to assess variability in “permanent employment” among white collar and blue collar employees in firms of different sizes, independent from their variability in the timing of interfirm job separations.

ISSN:0162-1459    

DOI:10.1080/01621459.1992.10475207

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

To improve verification of the Threshold Test Ban Treaty, the United States and Russia have embarked on an effort to make on-site yield measurements of each other's nuclear tests. Beyond their direct use in verification, these measurements also may prove useful in calibrating a monitoring system based on seismic magnitudes. The relative merits of seismic monitoring vis-a-vis on-site measurement have been at the core of a long-standing controversy. Many seismic verification problems hinge on statistical issues, including linear calibration based on a small data set and the formal use of expert opinion.

ISSN:0162-1459    

DOI:10.1080/01621459.1992.10475208

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Accurate estimation of price indices for residential property is an essential feature of real estate research, especially in view of recent efforts to forecast price trends for the 1990s. In this article, price trends are estimated by using the sales price, assessed value and date of sale for every residential property transaction between independent parties. This assessed value (AV) methodology is compared to the repeat sales (RS) method. This article develops a simple method for correcting the effect of the measurement errors associated with assessed value. We demonstrate that the large samples available with the AV method allow the measurement error problem to be reduced to negligible proportions. Using data on the Hartford, Connecticut metropolitan area, we find that price trends estimated from the AV and RS methods are substantially similar over a seven-year period. But the RS method is inefficient because it uses a relatively small subset of the data. Our results indicate that it remains inefficient when the researcher has a dataset much richer in repeat sales than ours.

ISSN:0162-1459    

DOI:10.1080/01621459.1992.10475209

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A data set consisting of 143 rankings of 10 occupations from a survey of Goldberg has been analyzed in a number of recent papers. The purpose of this paper is to use so-called “nested orthogonal contrasts” of the occupations to gain further insight into the data. A contrast is a comparison of subsets of the occupations based on their relative ranks; contrasts are orthogonal if the comparisons they represent are not confounded. Various models based on sets of orthogonal contrasts—including contingency table models, models analogous to those of Fligner and Verducci, and latent class models—are applied to the data. It is found that there are three main groups of occupations based on overall prestige, and within each group are distinctions between managerial and technical occupations.

ISSN:0162-1459    

DOI:10.1080/01621459.1992.10475210

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

We use Bayes factors to compare two alternative characterizations of human working memory load in their ability to predict errors in database query-writing tasks. The first measures working memory load by the number of different features each task contains, while the second attempts instead to measure the complexity of the task by giving more weight to features that require more mental time for their correct execution. We reanalyze data from a previously conducted experiment using two logistic regression models with random subject effects nested within an experimental condition factor. The two models have alternative covariates based on the alternative measures of working memory load. We construct prior distributions based on our subjective knowledge gleaned from related experiments, providing details of the elicitation process. We examine sensitivity of our results to the effects of prior misspecification and case deletion. Asymptotic approximations are used throughout to facilitate computations. Finally, we comment on the strengths and limitations of the approach in light of our experience.

ISSN:0162-1459    

DOI:10.1080/01621459.1992.10475211

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

We present a model in which compulsory school attendance laws, which typically require school attendance until a specified birthday, induce a relationship between years of schooling and age at school entry. Variation in school starting age created by children's dates of birth provides a natural experiment for estimating the effect of age at school entry. Because no large data set contains information on both age at school entry and educational attainment, we use an instrumental variables (IV) estimator with data derived from the 1960 and 1980 Censuses to estimate and test the age-at-entry/compulsory schooling model. In most IV applications, the two covariance matrices that form the estimator are constructed from the same sample. We use a method-of-moments framework to discuss IV estimators that combine moments from different data sets. In our application, quarter of birth dummies are the instrumental variables used to link the 1960 Census, from which age at school entry can be derived for one cohort of students, to the 1980 Census, which contains educational attainment for the same cohort of students. The results suggest that compulsory attendance laws constrain roughly 10% of students to stay in school.

ISSN:0162-1459    

DOI:10.1080/01621459.1992.10475212

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The recent discovery of hypervariable regions of the human genome provides scientists with an important new tool for forensic inference. The DNA data obtained from these hypervariable regions have been dubbedDNA fingerprints. Despite the potential power of DNA fingerprints, their use has been fraught with controversy, deriving in part from a lack of statistical methods to summarize the information contained in a DNA fingerprint. This article provides such a method, useful for forensic inference in criminal (e.g., murder or rape) and civil cases (e.g., paternity). The major difficulty with DNA fingerprint data is that the alleles (distinct DNA fragment sizes) are not observed; rather, one observes measurements of the DNA fragments with substantial error. When measurement error is superimposed on the discrete allele distribution, the fragments follow a mixture distribution. Consequently, our first step for forensic inference was to estimate the mixing distribution. With an estimate of the allele distribution, we summarize the information contained in a particular DNA fingerprint as the likelihood that the suspect and evidentiary samples are from the same individual versus the likelihood that they are from two different individuals. The informativeness of DNA fingerprint loci can be determined using Bayes risk methods. The methods we suggest are illustrated with a data set of DNA fragments from two hypervariable regions of the human genome (two loci, D2S44 and D17S79). Our results indicate that DNA fingerprinting can indeed by a very powerful tool for forensic inference.

ISSN:0162-1459    

DOI:10.1080/01621459.1992.10475213

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor