On testing hypotheses regarding a class of covariance structures

Let x be ap-component random variable having a multivariate normal distribution with covariance matrix . In this paper, we consider the problem of testing hypotheses of the formH ₀: =b ₁₁ + +b _{m m} , whereb _i 's are unknown scalars, and _i 's are a set of known and simultaneously diagonalizable matrices. This problem has both psychometric and statistical interest, and its basic theory is developed here. Besides, the problem of obtaining likelihood-ratio statistic for testingH ₀ is studied, and the statistic obtained in a special case.     

NOTE ON THE DOUBLE CENTERING OF DICHOTOMIZED MATRICES

A method is described for the double centering of dichotomized score matrices. It is based on a modification of the r _s coefficient of Guilford in which a second set of values, based on the reversed scoring of the original set, is used. A comparison of indices from matrices centered in such a manner, with some coefficients customarily obtained from score matrices, is presented.     

Changes in Academic Performance in the Junior High School

This study was designed to determine the relationships between changes in academic performance and intellective and non-intellective factors. Seventh grade students attending five junior high schools, who had attended selected elementary schools, were tested with the Personal Values Inventory (PVI), a test of academic motivation, shortly after the first seventh-grade marking period. School marks at that marking period and those received the previous year were procured from a self-report included in the PVI. All students had taken the California Achievement Test Battery and Mental Maturity Test as well as the Scholastic Testing Service Work-Study Skills Test in the sixth grade. Factor analysis identified four factors in both boys and girls: intelligence-achievement, academic motivation, academic plans, and youth-culture involvement. While intelligence was found to be mainly unrelated to the criterion, the non-intellective factors, especially academic motivation, bore significant relationships to the changed performance.     

Short-term recognition memory for single letters and phonemic similarity of retroactive interference

Copying 12 letters produces more retroactive interference in recognition memory for a single letter when the interference letters possess a vowel sound in common with the letter to be remembered than when they do not. Compared to interference lists that do not include the presented letter, inclusion in the interference list of the letter to be remembered improves recognition memory when the other interference letters have no vowel sound in common with the letter to be remembered, but not otherwise. False recognition rates are greater when the test letter contains a vowel sound in common with the presented letter than when the vowel sounds of these two letters are different. The findings are in complete accord with analogous findings for short-term recall and indicate that short-term recognition memory uses the same phonemic-associative memory system as short-term recall.     

Negative recency and event-dependence

In a two-choice situation with event-probabilities of 0.67 and 0.33, recency effects were studied as a function of (a) event-dependence and (b) fore-knowledge of event-probabilities. The following conclusions are drawn: (1) Belief in some kind of event-dependence is a necessary condition for the occurrence of negative recency; (2) Foreknowledge of the event-probabilities does not affect recency phenomena; (3) The behaviour of subjects in the two-choice situation, is less irrational than some writers have claimed.