Empirical validation of discrepancy formulae in the diagnosis of learning disabilities

Abstract

The Education for All Handicapped Children Act has established a "severe discrepancy between ability and achievement" as the predominant model for diagnosing learning disabilities in the United States. The Act, however, did not operationalize some of the variables used to calculate a severe discrepancy, including appropriate measures of ability and achievement, magnitude of the necessary discrepancy, and means of comparing test results from different instruments. The present study systematically manipulates these variables to determine their effects upon the types of subjects who are diagnosed as LD, and examines the validity of diagnosis by the resultant discrepancy formulae.