The possible biasing effects of attrition of subjects in longitudinal experiments is a problem to which social science researchers and evaluators rarely attend. A study of research on Project Follow Through, however, revealed few differences in family income or pretest scores, between students who dropped out of treatment and of comparison groups.…

A general interest in attrition, or loss of units from a study, stems in part from the observation that the infrequency of attention to attrition exacerbates problems of data interpretation. As a substudy of the national evaluation of Project Follow Through, the potential biasing effects of attrition of subjects from the sites were investigated.…

Follow Through is a longitudinal program instituted by the U.S. Office of Education in which a variety of curriculum models have been implemented in a number of locations nationwide. Because services are provided from kindergarten through third grade, many children enter and leave the program at points not coterminous with the treatment itself.…