Working Paper: NBER ID: w16238
Authors: James J. Heckman; Seong Hyeok Moon; Rodrigo Pinto; Peter A. Savelyev; Adam Yavitz
Abstract: Social experiments are powerful sources of information about the effectiveness of interventions. In practice, initial randomization plans are almost always compromised. Multiple hypotheses are frequently tested. "Significant" effects are often reported with p-values that do not account for preliminary screening from a large candidate pool of possible effects. This paper develops tools for analyzing data from experiments as they are actually implemented. We apply these tools to analyze the influential HighScope Perry Preschool Program. The Perry program was a social experiment that provided preschool education and home visits to disadvantaged children during their preschool years. It was evaluated by the method of random assignment. Both treatments and controls have been followed from age 3 through age 40. Previous analyses of the Perry data assume that the planned randomization protocol was implemented. In fact, as in many social experiments, the intended randomization protocol was compromised. Accounting for compromised randomization, multiple-hypothesis testing, and small sample sizes, we find statistically significant and economically important program effects for both males and females. We also examine the representativeness of the Perry study.
Keywords: Social Experiments; Early Childhood Education; Perry Preschool Program; Randomization; Multiple Hypothesis Testing
JEL Codes: C93; I21; J15
Edges that are evidenced by causal inference methods are in orange, and the rest are in light blue.
| Cause | Effect |
|---|---|
| compromised randomization (C90) | validity of previous analyses (C52) |
| correcting estimated treatment effects (C22) | more accurate inference regarding treatment effects (C22) |
| controlling for imbalances by conditioning on covariates (C32) | more accurate inference regarding treatment effects (C22) |
| Perry program (C88) | meaningful impacts on participants (C90) |
| correcting for selective reporting (C52) | substantial program effects (I24) |
| accounting for compromised randomization (C90) | strengthens evidence for important program effects (I24) |
| Perry participants (C90) | representativeness of a low-ability disadvantaged African American population (I24) |