On the occasion of Psychometrika's fiftieth anniversary, the past twenty-five years' developments in mental test theory are reviewed. Psychometrika articles treating topics in test theory are listed in a bibliography. (Author/LMO)

Paper is concerned with the hypothesis that two variables have a perfect disattenuated correlation, hence measure the same trait except for errors of measurement. (Author/RK)

This paper proposes a general model for free-response data collected for measuring a specified unidimensional psychological process; systematizes situations which vary with respect to the scoring level of items; and finds out general conditions for the operating characteristic of an item response category to provide a unique maximum likelihood…

Significant to a latent trait or item response theory analysis of a mental test is the determination of exactly what is being quantified. The following are practical problems to be considered in the formulation of a good theory: (1) deciding whether two tests measure the same trait or traits; (2) analyzing the relative contributions of a pair of…

The difficulties in comparing profile variability (a measure of test scatter) are briefly discussed and the limitations of current techniques pointed out. Test scatter is defined as individual variation in test scores between or within various psychological and educational tests. Currently, no statistical technique for the comparison of profile…

An attempt is made to indicate why the concept of "true score" naturally leads to the belief that test validity must increase with an increase in test and/or average item reliability, and why this is correct for the classical single-factor model first introduced by Spearman. The statistical model used by Loevinger is introduced to…

We concern ourselves with the hypothesis that two variables have a perfect disattenuated correlation, hence measure the same trait except for errors of measurement. This hypothesis is equivalent to saying, within the adopted model, that true scores of two psychological tests satisfy a linear relation. Statistical tests of this hypothesis are…

The previous theoretical development of the Poisson process as a strong model for the true-score theory of mental tests is discussed, and additional theoretical properties of the model from the standpoint of individual examinees are developed. The paper introduces the Erlang process as a family of test theory models and shows in the context of…

Some stochastic approximation procedures are considered in relation to the problem of choosing a sequence of test questions to accurately estimate a given examinee's standing on a psychological dimension. Illustrations are given evaluating certain procedures in a specific context. (Author/CK)

This paper models the educational process by a system of simultaneous equations. The endogenous variables (educational outputs) are a pupil's achievement, participation in a college preparatory program, need for achievement (aspirations), demonstrated motivation (effort), expectations, self-esteem, belief in his ability to control his environment…