title: Comparing two independent incidence rates using conditional and unconditional exact tests.
abstract: Several unconditional exact tests, which are constructed to control the Type I error rate at the nominal level, for comparing two independent Poisson rates are proposed and compared to the conditional exact test using a binomial distribution. The unconditional exact test using binomial p-value, likelihood ratio, or efficient score as the test statistic improves the power in general, and are therefore recommended. Unconditional exact tests using Wald statistics, whether on the original or square-root scale, may be substantially less powerful than the conditional exact test, and is not recommended. An example is provided from a cardiovascular trial.
authors.affiliation: TAP Pharmaceutical Products, Inc., Lake Forest, IL 6004, USA. cong.han@tap.com
authors.forename: Cong
authors.initials: C
authors.lastname: Han
mesh_terms: D002986:Clinical Trials as Topic / Q000706:statistics & numerical data / Q000639:trends; D015331:Cohort Studies; D006801:Humans; D015994:Incidence; D015233:Models, Statistical; D012107:Research Design / Q000639:trends; D013223:Statistics as Topic / Q000379:methods / Q000639:trends*