Computing Theoretical Rates of Part C Eligibility Based on Developmental Delays

Part C early intervention is a nationwide program that serves infants and toddlers who have developmental delays. This article presents a methodology for computing a theoretical estimate of the proportion of children who are likely to be eligible for Part C services based on delays in any of the 5 developmental domains (cognitive, motor, communication, social-emotional and adaptive) that are assessed to determine eligibility. Rates of developmental delays were estimated from a multivariate normal cumulative distribution function. This approach calculates theoretical rates of occurrence for conditions that are defined in terms of standard deviations from the mean on several variables that are approximately normally distributed. Evidence is presented to suggest that the procedures described produce accurate estimates of rates of child developmental delays. The methodology used in this study provides a useful tool for computing theoretical rates of occurrence of developmental delays that make children candidates for early intervention.