Bruce Bloxom

Constrained multidimensional scaling inN spaces

A gradient method is used to obtain least squares estimates of parameters of them-dimensional euclidean model simultaneously inN spaces, given the observation of all pairwise distances ofn stimuli for each space. The procedure can estimate an additive constant as well as stimulus projections and the metric of the reference axes of the configuration in each space. Each parameter in the model can be fixed to equal some a priori value, constrained to be equal to any other parameter, or free to take on any value in the parameter space. Two applications of the procedure are described.

Considerations in psychometric modeling of response time

Semiparametric models express a set of distributions of event times in terms of (a) a single parameter which varies across distributions and (b) a single function which does not vary across distributions and which has an unspecified form. These models appear to be attractive alternatives to parametric models of response times in psychometrics. However, our use of such models may require incorporating additional functions which do not vary across distributions and may require expressing the models in terms of the joint distribution of response class and response time.

Estimating response time hazard functions: An exposition and extension

Abstract The hazard function of a response time distribution describes the temporal dimension of a response process and completely characterizes the distribution. The function can be estimated by a quadratic spline which is constrained to have one of a number of simple functional forms. The estimator can also be employed when the response time is an unobserved component in a parallel or serial pair of processes.

Alternative approaches to factorial invariance

Special cases of the factor analysis model are developed for four selection situations. Methods are suggested whereby parameters in each case can be estimated using a maximum likelihood procedure recently developed by Jöreskog. Also, a numerical illustration is presented for each case.

The simplex in pair comparisons

A model of individual differences in pair comparisons is developed, assuming the affective values to have a quasi-simplex structure. Procedures for fitting the model to data are suggested. An empirical example is given for one of the procedures.

Estimating an Unobserved Component of a Serial Response Time Model.

A method is developed for estimating the response time distribution of an unobserved component in a two-component serial model, assuming the components are stochastically independent. The estimate of the components density function is constrained only to be unimodal and non-negative. Numerical examples suggest that the method can yield reasonably accurate estimates with sample sizes of 300 and, in some cases, with sample sizes as small as 100.

A fourier integral density estimate: a Monte Carlo study

Davis (1977) proposed the use of a kernel density estimate which is the sample characteristic function integrated over (-A(n) , A(n)), where A(n) is chosen to minimize the mean integrated square error of the estimate. The scalar, A(n), is determined by the sample size and the population characteristic function. This paper investigates, in a Monte Carlo study, the mean integrated square error obtained under a procedure suggested by Davis (1977) for estimating A(n) when the population characteristic function is unknown.

James Neal Butcher (Ed.). MMPI: Research Developments and Clinical Applications. New York: McGraw-Hill, 1969. Pp. xiv + 402.

even though the book is replete with problems (both worked and left for the student to work) interspersed through the text and at the ends of the chapters. Bashaw’s basic goal is to establish understanding. Outstandingly good examples of instances where he achieves this goal are his explanation of the placement of the decimal point in dividing decimal fractions and his presentation of what is involved in calculating the inverse of a matrix. In the former case, he appeals in a fairly rigorous but intuitively attractive way to the nature of the base 10 number system. In the latter instance, Bashaw illustrates