Estimation and Identification of the Complier Average Causal Effect Parameter in Education RCTs

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 article uses a causal inference and instrumental variables framework to examine the identification and estimation of the CACE parameter for two-level clustered RCTs. The authors use data from 10 large-scale RCTs to compare significance findings for the CACE estimator based on correct variance formulas with those based on commonly used formulas that ignore certain sources of error. These formulas lead to very similar significance findings.