Most of the tests in the literature have been proposed for this situation, so we shall reserve the notation H0 for the hypothesis: Tests for this hypothesis are those discussed throughout most of this chapter, although authors return to Case 3 in. One group which is treated mainly in this chapter are tests based on spacings between uniforms since such spacings are exponentials and these tests have arisen mostly in connection with tests of H0. Finally, the authors should note that powerful tests on lifetimes will be powerful tests on any general random sample, regardless of its source. The first spacings statistic which authors discuss was introduced by Greenwood in connection with tests on a series of events; specifically, on the incidence of a contagious disease. Test statistics should be regarded as giving information about the data and their parent population, rather than as tools for formal testing procedures.