A new method of analysis was used in the Michigan Educational Assessment Program to test minimum competencies in fourth grade reading achievement. This technique permitted a substantial decrease in testing time and costs. The original test consisted of 95 items measuring 19 objectives; mastery was indicated by correct responses to four out of the five items measuring each objective. Data from those 1,096 students whose raw scores were between 36 and 83 were re-analyzed. Several tests were used to determine which items were acceptable for analysis using the Rasch model. It was felt that the 95 items fit the Rasch model, and that the item calibrations would yield standard log achievement scores (SLAs) that would accurately summarize where students fell on the latent trait measured by the test. These SLAs provided essentially the same information as the number of objectives mastered, with a shorter test. For most students, the items were relatively simple given student achievement levels; therefore, the amount of information provided was slight. A short, ten-item test was developed; analysis indicated that it imposed a more rigid criterion than the longer test. Mastery decisions using the short test led to 14.9% fewer Type II errors (false negatives) and 1.6% more Type I errors (false positives). (GDC)