An analysis of difference score reliabilities on three measures with a sample of low‐achieving youngsters

A common practice in the field of learning disabilities is analysis of ability‐achievement discrepancies. The reliability of discrepancy scores is an important statistic in such decision making. In this study, selected ability and achievement devices were administered to a sample of low achievers (N = 99), and the reliability of various difference scores was analyzed. In all cases, the reliabilities of difference scores were moderately high. Reliabilities of differences for devices normed on the same population and differences for devices normed on different populations were comparable. These results are discussed in light of current psychometric practices.