There is growing recognition that the bulk of the traditional, nofm-referenced tests fail to he@ teachers make instructional decisions. In rejecttng these measures, diagnosticians and teachers alike are seeking strategies for identifying and dire&y remediating mistakes students make in W m etic computation. n7is article presents a stepby-step series of operations for analyzing and categorizing aritf?metic errvrs, for selecting cormthe strategies, and for applying peer-referenced standards to judge the performance of special-needs students.