The effects of day care 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 since $1972$. 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.

(a) Explain the purpose of each of the three experimental design principles.

(b) Describe how each of these principles was used in this study.

Experiment was done on $111$children since $1972$. They were healthy but low income infants.

Infants received nutritional supplements from social workers.

Rules of experimental design are:

• Lurking variables.
• Random assignment
• Duplication

It is mandatory to use two classes to find result of lurking variables.

With random assignment, we need to build equal classes before treatment. To make sure that not chance variable but treatment bought difference in results.

Results are monitored using two classes for comparison with lurking variables. Children are equally divided in two groups.

Trial was done on $111$students. Replication is important to ensure that responses are due to therapy, supplements and help offered to them socially.