Objectives: This study derives the statistical power of the common hit rates test of taste-based discrimination in police searches. It also identifies search intensity as a source of bias in the test and proposes a simple empirical adjustment to account for the bias. Methods: Data simulations, along with two empirical applications to motor vehicle search data, display the practical importance of both statistical power and search intensity bias in the hit rates test. Results: Statistical power varies markedly with the parameters of the application. Differential search intensity across groups will bias results, but the simple empirical adjustment provides a valid test when the data contain a discrete indicator of search intensity. In the empirical applications, unadjusted and adjusted tests differ in their conclusion of whether police discrimination exists. Conclusions: For the presentation of multiple hit rates tests, statistical power should be reported with p-values. Theoretical bounds on search intensity bias are wide, and the bias can persist for any sample size. Hit rates tests should therefore be interpreted with caution when data contain no indicator of search intensity.
- Motor vehicle
- Racial bias
- Traffic stop
ASJC Scopus subject areas
- Pathology and Forensic Medicine