The reliability coefficient is unlike other measures of correlation in that it is a quantitative statement of an act of judgment,—usually the test maker's, — that the things correlated are similar measures. Attempts to divorce it from this act of judgment are misdirected, just as would be an attempt to eliminate judgment of sameness of function of items when a test is originally drawn up. A “coefficient of cohesion,” entirely devoid of judgment, measuring the singleness of test function is proposed as an essential datum with reference to a test, but not as a substitute for the similar-form reliability co-efficient.

This paper is concerned particularly with certain regression effects which appear whenever matched groups are drawn from populations which differ with regard to the characteristics being studied. It is shown that regression will produce systematic differences between specifically matched. The size and direction of these differences depends upon the differences between the parent populations both in the matching and in the experimental variables and upon the correlation between the matching and experimental variables. Formulas are presented for estimating the expected regression effect. Several alternative procedures are suggested for avoiding the erroneous conclusions which the regression effect is likely to suggest.

In this article are presented a number of unusual achievement test exercises of both the essay and the objective types. These exercises may suggest to others engaged in the construction of achievement tests certain forms which they may find useful either as models or as points of departure in the invention of new forms. The article also calls attention to certain problems which must be solved if achievement testing is to have a sound, scientific basis.

Previously derived equations for the control of the behavior of one social group by another are developed further. Cases of interaction of three social classes are studied, and the variation of such an interaction with time is investigated. A previously derived equation for the ratio of urban to rural population is generalized, and a theory of interaction of industrial and agricultural classes is outlined. Some of the theoretically derived equations are compared with available sociological data and found in fair agreement.

In this article the authors examine the effect of including alternate test forms in a factor matrix upon the validity of the resultant factor loadings, finding that in this particular instance the effect is negligible. Comparisons of the factor loadings derived from matrices in which only one of the alternate test forms is included with those in which both forms are included reveal practically no difference in the magnitude of either the original or rotated factor loadings, or in that of the computed communalities.

Controlled by microphone, photocell, or keys, the described instrument operates a chronoscope, chronograph, etc., together with a projector, bell, light, or other stimulus requiring up to 200 watts.

A method of computing biserial coefficients of correlation through the use of punch card tabulating equipment is presented. Each item is assigned a separate column and successes are punched 1. By arranging the cards on the criterion variable and obtaining progressive sums on several columns simultaneously, it is possible to obtain data for several correlations in one run of the cards through the machine.