An Empirical Study of the Stability of a Group Mean in Relation to the Distribution of Test Items Among Pupils

Abstract

Two alternative procedures of measuring group achievement under limited testing time are defined and empirically compared with respect to their efficiency in estimating a group mean and ranking a number of groups. The procedures are (A) administering the same set of items to each student in a group, and (B) administering a different set of items to each student in the group. Item scores on a college mathematics examination are employed in the comparisons.

Estimating Norms by Item-Sampling

“…The effectiveness of item-sampling for estimating a group's mean score was investigated in an earlier study (Johnson & Lord, 1958). Now the attempt is made to estimate the entire frequency distribution of scores, rather than just the group mean.2…”