Modeling the impacts of child care quality on children's preschool cognitive development.

The National Institute of Child Health and Human Development (NICHD) Study of Early Child Care compared 3 statistical methods that adjust for family selection bias to test whether child care type and quality relate to cognitive and academic skills. The methods included: multiple regression models of 54-month outcomes, change models of differences in 24- and 54-month outcomes, and residualized change models of 54-month outcomes adjusting for the 24-month outcome. The study was unable to establish empirically which model best adjusted for selection and omitted-variable bias. Nevertheless, results suggested that child care quality predicted cognitive outcomes at 54 months, with effect sizes of .04 to .08 for both infant and preschool ages. Center care during preschool years also predicted outcomes across all models.