Boston Review — Charles Murray Responds to James J. Heckman: "Perry Preschool and the Abecedarian Project. The samples were small. Perry Preschool had just 58 children in the treatment group and 65 in the control group, while Abecedarian had 57 children in the treatment group and 54 in the control group. In both cases the people who ran the program were also deeply involved in collecting and coding the evaluation data, and they were passionate advocates of early childhood intervention. These shortcomings do not automatically disqualify the results, but think of it this way: if the case against the efficacy of early childhood interventions rested on two studies with small samples conducted by people who were openly hostile to such interventions, no one would pay any attention to them."
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