Studies designed to assess the efficacy of interventions with organically impaired infants in terms of how well the experimental designs used controlled for threats to interval validity were analyzed. The use of methodologically more rigorous designs in evaluation studies is recommended to prevent or ameliorate the adverse effects of…

Studies examining the effectiveness of early intervention for infants and children with organic impairment and and developmental delay were reviewed using recently developed quantitative methods. Results suggest an accurate interpretation of the early intervention research literature cannot be made without consideration of specific design…