摘要:

This article illustrates basic statistical techniques for studying coincidences. These include data-gathering methods (informal anecdotes, case studies, observational studies, and experiments) and methods of analysis (exploratory and confirmatory data analysis, special analytic techniques, and probabilistic modeling, both general and special purpose). We develop a version of the birthday problem general enough to include dependence, inhomogeneity, and almost and multiple matches. We review Fisher's techniques for giving partial credit for close matches. We develop a model for studying coincidences involving newly learned words. Once we set aside coincidences having apparent causes, four principles account for large numbers of remaining coincidences: hidden cause; psychology, including memory and perception; multiplicity of endpoints, including the counting of “close” or nearly alike events as if they were identical; and the law of truly large numbers, which says that when enormous numbers of events and people and their interactions cumulate over time, almost any outrageous event is bound to occur. These sources account for much of the force of synchronicity.

ISSN:0162-1459    

DOI:10.1080/01621459.1989.10478847

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The recent literature on evaluating manpower training programs demonstrates that alternative nonexperimental estimators of the same program produce an array of estimates of program impact. These findings have led to the call for experiments to be used to perform credible program evaluations. Missing in all of the recent pessimistic analyses of nonexperimental methods is any systematic discussion of how to choose among competing estimators. This article explores the value of simple specification tests in selecting an appropriate nonexperimental estimator. A reanalysis of the National Supported Work Demonstration data previously analyzed by proponents of social experiments reveals that a simple testing procedure eliminates the range of nonexperimental estimators at variance with the experimental estimates of program impact.

ISSN:0162-1459    

DOI:10.1080/01621459.1989.10478848

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

ISSN:0162-1459    

DOI:10.1080/01621459.1989.10478849

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

ISSN:0162-1459    

DOI:10.1080/01621459.1989.10478850

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

ISSN:0162-1459    

DOI:10.1080/01621459.1989.10478851

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Thetdistribution provides a useful extension of the normal for statistical modeling of data sets involving errors with longer-than-normal tails. An analytical strategy based on maximum likelihood for a general model with multivariateterrors is suggested and applied to a variety of problems, including linear and nonlinear regression, robust estimation of the mean and covariance matrix with missing data, unbalanced multivariate repeated-measures data, multivariate modeling of pedigree data, and multivariate nonlinear regression. The degrees of freedom parameter of thetdistribution provides a convenient dimension for achieving robust statistical inference, with moderate increases in computational complexity for many models. Estimation of precision from asymptotic theory and the bootstrap is discussed, and graphical methods for checking the appropriateness of thetdistribution are presented.

ISSN:0162-1459    

DOI:10.1080/01621459.1989.10478852

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

In medical studies, the computation of a meaningful incidence rate frequently demands adjustment for covariates. One means for achieving such adjustment isstandardization.The (directly) standardized rate is calculated by using the appropriate weighted average of rates overstratadetermined by the covariates. Thus strata formation is crucial in obtaining good results. This article compares three competing methods for stratification using data from a drug study in which the incidence rate of a certain side effect is of interest. The techniques examined are (a) contingency-table cell aggregation, (b) classification trees, and (c) logistic regression. The relative merits of the three methods are discussed.

ISSN:0162-1459    

DOI:10.1080/01621459.1989.10478853

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A binomial regression functionp(x, θ) models the probability ofrjsuccesses innjtrials as a function of the values of an observed covariatexjand/or a latent variableθj(j= 1, …,J). This article explores the use of monotone regression splines to definep, and applies them to the representation of test items as functions of examinee ability. Some illustrative data suggest that the flexibility of monotone splines permits the detection of item characteristics not observable using logistic-based or log-linear approaches. A simulation study indicates that estimates of both item-characteristic curves and ability are reasonably precise for numbers of items and examinees typical of large university lectures. Given a set of such binomial regression functions, it can be useful to study the principal components of functional variation. The extension of multivariate principal-components analysis to permit the analysis of many item-characteristic curves is described.

ISSN:0162-1459    

DOI:10.1080/01621459.1989.10478854

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The two-phase sampling design has been traditionally used in ecology applications to estimate age composition. With regard to both economic and statistical considerations, however, the two-phase design may yield estimates of the age composition that are no better than can be obtained using simple random sampling. This article shows that the optimality of the two-phase sampling design depends upon (a) survey objectives, (b) per-unit sampling costs, and (c) the predictive power of stratum membership on age. Methods are given for determining whether two-phase sampling yields better estimates of the age composition than simple random sampling, accounting for (a), (b), and (c).

ISSN:0162-1459    

DOI:10.1080/01621459.1989.10478855

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A magazine-exposure model that mixes Klotz's (1973) dependent Bernoulli-trials model for nonsubscribers with a degenerate distribution for subscribers is proposed. LetXi= 1 if a person reads an issue of a particular magazine and 0 otherwise. Klotz's parameterization is Pr(Xi= 1) =pand Pr(Xi= 1 |Xi–1= 1) = λ fori= 1, …,k.Using the Markov assumption he obtains the joint distribution ofR= Σki=2Xi–1Xi, S= Σki=1Xi, andT = X1+Xk, of which we are interested in the marginal distribution ofS, the total number of issues a person reads. It is expected thatpwill be low for nonsubscribers but high for subscribers, so this heterogeneity is modeled by mixing Klotz's Markov model with a point mass of magnitude π at the pointS=k.Maximum likelihood estimates ofp, λ, and π are used to fit the Markov mixture model to 40 magazines from a large print-media survey. The proposed model is shown to give a much better fit to these data than the beta-binomial model, the most popular nonproprietary magazine model, and a generalization of the beta-binomial model.

ISSN:0162-1459    

DOI:10.1080/01621459.1989.10478856

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor