ABSTRACT
In Section 4.9, we indicated the importance of testing one-tailed null hypotheses and made the cr ucial distinction between “tests of one-tailed null hypotheses” and “tests of two-tailed null hypotheses that use a onetailed test statistic.” The latter are frequently called “one-tailed tests” but in fact this terminology might be misleading because these tests really concern two-tailed null hypotheses. In this chapter, we elaborate on the idea already introduced in Section 4.9 of testing genuine one-tailed null hypotheses and extend this idea to testing null hypotheses about ef fect magnitude.
