Obstacles in Using Randomization Tests in Single-Case Experimentation

Edgington has just proposed the use of randomization tests for single-case experimental designs. The specific tests presented require rapidly alternating treatments over time for a given subject. Although randomization tests may provide viable statistical options, several features of single-case research ordinarily would preclude their use. Characteristics of the interventions and responses that are encompassed by the substantive areas of single-case research are likely to preclude shifting rapidly from one treatment to another on a randomized schedule. Also, the possibility of multiple-treatment interference may be especially acute with randomization tests. Finally, the use of randomization tests may compete with the logic of single-case experimental designs. The present paper discusses both applied and methodological restrictions on the use of randomization tests.