摘要:

The mental processes involved in performing some tasks can be represented as directed arcs in an acyclic network. A path directed from the head of one arc to the tail of another indicates that the process represented by the first arc must be executed prior to the process represented by the second arc. If there is no directed path from one arc to another, the corresponding processes can be executed concurrently. Information about the arrangement of processes in an acyclic network can be found from the effects on response times of factors selectively influencing the processes. The methodology was developed earlier for critical path networks, in which a process begins execution when all its immediate predecessors have finished. This paper considers shortest path networks, in which a process begins execution as soon as any immediate predecessor is finished. Results analogous to those for critical path networks are reported. New results are presented enabling investigators to distinguish sequential and concurrent processes in both critical path and shortest path networks. This information is sufficient to construct an acyclic network representing the processes. Further, by examining the effects of selectively influencing processes, one can determine whether a task network is a critical path network or a shortest path network.

ISSN:0007-1102    

DOI:10.1111/j.2044-8317.1993.tb00999.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The problem of how a consistent sensory input can be given an invariant name is addressed within the framework of nonlinear psychophysical theory. In order to link sensory transduction processes to cognitive operations an extension of purely psychophysical modelling is used. A hybrid model of sensory switching, produced by injecting a Λ recursion into a non‐Lipschitzian dynamics evolved by Zak, has the capacity to differentiate inputs and encode inputs into classes, in a form that makes vector inputs to neural networks possible. This is a necessary precursor to learning new sensory‐verbal mappings. The distinction between using piecewise linear models and using continuous nonlinear dynamics in theory construction is emphas

ISSN:0007-1102    

DOI:10.1111/j.2044-8317.1993.tb01000.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

This paper considers the circumstances under which qualitative generalizations from statistical tests are possible. When observations from different conditions are assumed to be identically distributed except for a location parameter, then any difference that is established between the conditions will be entirely due to location. Furthermore, the direction of these differences will be independent of the statistic used, the scale of measurement or the shape of the distributions. This implies that significant differences between conditions generalize to latent variables (variables which are monotonie transformations of observed variables). Obtaining a significant difference between two conditions establishes the direction of that difference and obtaining significance in a test of differences between more than two conditions establishes a nonparametric correlation between the observed and population means. To make equivalent generalizations from main effects in factorial analyses of variance it must be assumed that the observations are random with respect to the other factors in the design. Correlation and regression analyses generalize to latent variables where all the variables are monotonically related. However, this implies that there is only one ordinally distinct latent variable. Where non‐monotonic relationships are possible and one distribution is treated as fixed, significant correlation and regression analyses do not generalize to latent variables. It is argued that while linear modelling may be an appropriate method of making quantitative predictions from a set of random variables, tests of differences are more interpretable than correlations where the aim is to study theoretically interesting latent variable

ISSN:0007-1102    

DOI:10.1111/j.2044-8317.1993.tb01001.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

A well‐known result is that the value of the standard error of the sample mean is sensitive to heavy tails (Tukey, 1960). In particular, moving slightly away from a normal distribution toward a heavier tailed distribution can increase the standard error by a considerable amount. As a result, methods for comparing means can have relatively low power. This problem is particularly serious in psychology because recent investigations indicate that the distributions associated with psychometric measures often have outliers and very heavy tails (Micceri, 1989; Wilcox, 1990a). One approach to this problem is to compare trimmed means instead. Yuen (1974) describes a method for comparing the trimmed means of two independent groups, and she demonstrated that her procedure can have considerably more power than Welch's test for means. This paper extends Yuen's solution to repeated measures and randomized block designs. Simulations indicate that the new procedure compares well to the usualFtest using the Huynh‐Feldt correction of the degrees of free

ISSN:0007-1102    

DOI:10.1111/j.2044-8317.1993.tb01002.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

In the linear regression problem M‐estimators are frequently applied as an alternative to least squares estimators to obtain robustness, when there are outliers in the dependent variable. When we allow for nonlinear transformations of the variables (Young, 1981), the effects of outliers can still be large. In this paper it is shown that M‐estimators can also be used for nonlinear multiple regression. Two types of M‐estimators are used: the Huber and biweight estimator.Permutation tests are applied to obtain significance levels for the multiple correlation coefficients. Furthermore, an exploratory procedure is proposed, which is useful in finding out which tuning constant is optimal for the given problem. In a Monte Carlo study the stability of the different solutions and the influence of the outliers is examined by using the jack‐knife. It was found that the biweight function was the most robust and eliminated the influence of the o

ISSN:0007-1102    

DOI:10.1111/j.2044-8317.1993.tb01003.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

This paper introduces a mixture regression model for the analysis and interpretation of multivariate count data in a heterogeneous population. The model is derived by specifying a regression relationship at the individual level between the choice data and a set of concomitant variables. A latent class representation is introduced to describe variations in the regression weights among individuals and to obtain a representation of the aggregate choice behaviour. An easy‐to‐implement EM algorithm is presented for parameter estimat

ISSN:0007-1102    

DOI:10.1111/j.2044-8317.1993.tb01004.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

A method is offered for orthogonal Procrustes rotation of two or more matrices with missing values, and an extension to Generalized Procrustes Analysis is given. The method is based on the idea that missing values, in arbitrary places, can be replaced by optimal values according to the least squares criterion. Commandeur has offered a method of orthogonal Procrustes rotation and Generalized Procrustes Analysis for the case where entire rows of the data matrices are missing. It is proved that our method yields essentially the same results as Commandeur's method, in that case. A simulation study for Procrustes rotation is described in which complete columns of matrices, derived from a common underlying structure, are deleted, and either replaced by zeros or estimated on the basis of the newly proposed method. In those conditions where the underlying structure can adequately be disentangled from the error, our method appears to recover the underlying structure more accurately than when the missing columns are replaced by zeros.

ISSN:0007-1102    

DOI:10.1111/j.2044-8317.1993.tb01005.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

For the analysis of variables of mixed measurement levels a class of methods can be used that is based on three‐way analysis of quantification matrices for nominal or quantitative variables. This class of methods incorporates some well‐known techniques but also offers a series of interesting new alternatives for the analysis of nominal or quantitative variables. Ordinal variables have received hardly any attention in this class of methods, and are usually treated as if they are quantitative variables. In the present paper this gap is filled by constructing quantification matrices for ordinal variables via optimal scaling of the ordinal variables, thus yielding optimal quantification matrices for these variables. Algorithms for this optimal scaling procedure are developed, and the optimal scaling procedures are compared to optimal scaling of ordinal variables in the context of principal components analysis and multidimensional scal

ISSN:0007-1102    

DOI:10.1111/j.2044-8317.1993.tb01006.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Biggins, Loynes&Walker (1986) considered the problem of scaling and combining examination marks from several papers to obtain transformed marks and an overall measure of each candidate's performance in the examination. Their approach is to obtain the transformations and the overall marks by the minimization of a suitably chosen loss function subject to a single constraint. In the main, following Broyden (1983), they consider the case where the allowed transformation is multiplication by a constant (which varies from paper to paper). This paper discusses the same problem but with a richer class of possible transformations, the main example being regression splines with end‐point restrictions. These end‐point restrictions will mean that the curve can be forced to preserve the mark range, by passing through (0, 0) and (100,100), for example. If grades rather than marks are returned the problem becomes the well‐studied one of scaling categorical attributes. Our formulation applies in this case also, allowing us to connect the proposals with existing scaling literature. The general issue of how to incorporate the expectation that transformation curves should not be too far from the 45° line is also addressed, with the device of using fictitious candidates, introduced by Bigginset al.(1986), being extended to this c

ISSN:0007-1102    

DOI:10.1111/j.2044-8317.1993.tb01007.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Book reviewed in this article:The Wave Theory of Difference and Similarity.ByStephen W. Link.Decision Analysis for Management Judgment.ByPaul Goodwin&George Wright.Summated Rating Scale Construction.ByP. E. Spector.Fundamentals of Item Response Theory.ByR. K. Hambleton, H. Swaminathan&H. J. Rogers.Latent Variable Models: An Introduction to Factor, Path, and Structural Analysis, 2nd ed.ByJ. C. Loehlin.Scale Development: Theory and Applications.ByRobert F. DeVellis.

ISSN:0007-1102    

DOI:10.1111/j.2044-8317.1993.tb01008.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY