Question: Distinguish between a one-tailed test and two-tailed test, and explain why a Type III error is possible only with one-tailed tests.
• Nondirectional (two-tailed) tests are hypothesis tests in which the alternative hypothesis is stated as not equal to (:t!=) a value stated in the null hypothesis. So we are interested in any alternative to the null hypothesis.
• Directional (one-tailed) tests are hypothesis tests in which the alternative hypothesis is stated as greater than(>) or less than(would have been significant in one tail, but the researcher retains the null hypothesis because the rejection region was placed in the wrong or opposite tail.