Optimum difficulty of group test items

Abstract

The problem was to find the best range of difficulty of test items, using predictive value as a criterion. Two groups of 240 college students were used. They were chosen to represent four levels of ability based on the Thorndike Examination score, Iowa Content Examination score, and average of freshman scholarship marks. Within the limits of the data presented, it appears that the test items having greatest predictive value lie within an area bounded by a point 30% above the most difficult end of the arbitrary scale and a point about 20% below the least difficult end. The midpoint of the best average predictive value lies near the mean of difficulty but toward the least difficult end of the arbitrary scale. (PsycInfo Database Record (c) 2022 APA, all rights reserved)