A more powerful test for comparing two Poisson means

The problem of hypothesis testing about two Poisson means is addressed. The usual conditional test (C-test) and a test based on estimated p-values (E-test) are considered. The exact properties of the tests are evaluated numerically. Numerical studies indicate that the E-test is almost exact because its size seldom exceeds the nominal level, and it is more powerful than the C-test. Power calculations for both tests are outlined. The test procedures are illustrated using two examples. (C) 2002 Elsevier B.V. All rights reserved.