Abstract
Leading researchers in the field of early intervention for children with special needs are advocating for the production of second-generation research to answer the question of which type of program works best for which group of children. The purpose of the present study was to respond to the second-generation research question by examining the differential effectiveness of an intensive, center-based early intervention program for three groups of participants with varying levels of impairment. Data were analyzed using three different approaches in order to shed light upon the appropriate use and selection of methods of examining child progress in early intervention programs. These three methods included rates of development during intervention (RDIs), residual gain scores, and a comparison of actual posttest scores to those predicted using pretest scores and based upon the assumption of constant and linear increments for all individuals. Findings revealed that in the cognitive, fine motor, gross motor, and receptive language domains, the groups of children with mild and moderate impairments developed at faster rates during intervention (higher RDIs) than did the group with more severe impairments. In the fine motor domain, the groups with mild and moderate impairments had statistically significantly higher residuals than did the group with severe impairments. No other findings were significant. Findings are discussed in terms of implications for program administrators, policymakers, and decision makers.