A RANKING VARIABLE ANALOGUE OF BISERIAL CORRELATION: IMPLICATIONS FOR SHORT‐CUT ITEM ANALYSIS

Abstract

The writer's purpose is to propose a new, easily calculable index of item discrimination for use in the validation of dichotomously scored items. The derivation of the index is discussed only briefly since this and other technical matters have been presented elsewhere (Glass, 1965). Computation of the index is illustrated. The strengths and weaknesses of the proposed index relative to several existing indices of item discrimination are discussed. Specifically, the nonparametric character of the index, its range, a significance test, and the problem of correcting for the overlap of item with total test score are touched upon.