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ERIC Number: ED504795
Record Type: Non-Journal
Publication Date: 2009-Apr
Pages: 60
Abstractor: As Provided
Technical Methods Report: Estimation and Identification of the Complier Average Causal Effect Parameter in Education RCTs. NCEE 2009-4040
Schochet, Peter Z.; Chiang, Hanley
National Center for Education Evaluation and Regional Assistance
In randomized control trials (RCTs) in the education field, the complier average causal effect (CACE) parameter is often of policy interest, because it pertains to intervention effects for students who receive a meaningful dose of treatment services. This report uses a causal inference and instrumental variables framework to examine the identification and estimation of the CACE parameter for two-level clustered RCTs. The report also provides simple asymptotic variance formulas for CACE impact estimators measured in nominal and standard deviation units. In the empirical work, data from ten large RCTs are used to compare significance findings using correct CACE variance estimators and commonly-used approximations that ignore the estimation error in service receipt rates and outcome standard deviations. Our key finding is that the variance corrections have very little effect on the standard errors of standardized CACE impact estimators. Across the examined outcomes, the correction terms typically raise the standard errors by less than 1 percent, and change p-values at the fourth or higher decimal place. Two appendixes are included: (1) Proof of Equation; and (2) Summary of Data Sources. (Contains 7 footnotes and 11 tables.)
National Center for Education Evaluation and Regional Assistance. Available from: ED Pubs. P.O. Box 1398, Jessup, MD 20794-1398. Tel: 877-433-7827; Web site:
Publication Type: Reports - Evaluative
Education Level: N/A
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: Institute of Education Sciences (ED), National Center for Education Evaluation and Regional Assistance
IES Funded: Yes