Do get-out-the-vote calls reduce turnout? The importance of statistical methods for field experiments

In their landmark study of afield experiment, Gerber and Green (2000) found that get-out-the-vote calls reduce turnout by five percentage points. In this article, I introduce statistical methods that can uncover discrepencies between experimental design and actual implementation. The application of this methodology shows that Gerber and Green's negative finding is caused by inadvertent deviations from their stated experimental protocol. The initial discovery led to revisions of the original data by the authors and retraction of the numerical results in their article. Analysis of their revised data, however, reveals new systematic patterns of implementation errors. Indeed, treatment assignments of the revised data appear to be even less randomized than before their corrections. To adjust for these problems, I employ a more appropriate statistical method and demonstrate that telephone canvassing increases turnout by five percentage points. This article demonstrates how statistical methods can find and correct complications of field experiments.