The one parameter latent trait theory of Georg Rasch has two assumptions: that student abilities can be measured on an equal interval scale, and that the success of a student with a given item is a function of student achievement and item difficulty. The grade four Michigan Educational Assessment Program reading test was designed to measure nineteen objectives with 95 items (five items for each objective). Mastery for each objective was defined as four correct out of five. The data analysis for this study consisted of separately analyzing the total score on the 95 items and the mastery scores on the 19 objectives, and placing both scores on the same Rasch model score scale. A table is presented showing the raw test score ranges for those students with various mastery scores. The author concludes that Rasch scaled scores would have provided more information than the mastery approach. (CTM)