Does day care help low-income children stay in school and hold good jobs later in life? The Carolina Abecedarian Project (the name suggests the ABCs) has followed a group of 111 children for over 40 years. Back then, these individuals were all healthy but low-income black infants in Chapel Hill, North Carolina. All the infants received nutritional supplements and help from social workers. Half were also assigned at random to an intensive preschool program. Results? Children who were assigned to the preschool program had higher IQ’s, higher standardized test scores, and were less likely to repeat a grade in school.

a. Explain how this experiment used comparison.

b. Explain the purpose of randomly assigning the infants to the two treatments.

c. Name two variables that were controlled in this experiment and why it was beneficial to control these variables.

d. Explain how this experiment used replication. What is the purpose of replication in this context?