The Phi Coefficient and Chi Square as Indices of Item Validity

Abstract

Two new methods of item analysis are described. One involves the computation of the ϕ coefficient (correlation of a fourfold point distribution) and the other involves chi square. The only data required are the proportions of passing individuals in the upper and lower criterion groups, for the determination of ϕ, and in addition, N , for the determination of chi square. Abacs are presented for graphic solution of the two indices of validity, and tests of significance are provided.