Seminar
William F. Rosenberger
SEQUENTIAL MONITORING OF RANDOMIZATION TESTS
Randomization provides a basis for inference, but it is rarely taken
advantage of. We discuss randomization tests based on the family of
linear rank tests in the context of sequential monitoring of clinical
trials. Such tests are applicable for categorical, continuous, and
survival time outcomes. We prove the asymptotic joint normality of
sequentially monitored test statistics, which allows the computation of
sequential monitoring critical values under the Lan-DeMets procedure.
Since randomization tests are not based on likelihoods, the concept of
information is murky. We give an alternate definition of randomization
and show how to compute it for different randomization procedures. The
randomization procedures we discuss are the permuted block design,
stratified block design, and stratified urn design. We illustrate these
results by reanalyzing a clinical trial in retinopathy.