  We consider the problem of generating confidence intervals in randomized
experiments with noncompliance. We show that a refinement of a
randomization-based procedure proposed by Imbens and Rosenbaum (2005) has
desirable properties. Namely, we show that using a studentized
Anderson-Rubin-type statistic as a test statistic yields confidence intervals
that are finite-sample exact under treatment effect homogeneity, and remain
asymptotically valid for the Local Average Treatment Effect when the treatment
effect is heterogeneous. We provide a uniform analysis of this procedure.
