A researcher evaluates a treatment effect using a one-tailed hypothesis test with α = .05,and the decision is to reject the null hypothesis.If the researcher switched to a two-tailed test using the same sample,what decision would be made?
A)Definitely reject the null hypothesis with either α = .05 or with α = .01
B)Definitely reject the null hypothesis with α = .05 and maybe reject with α = .01
C)Might reject the null hypothesis with α = .05 but might not
D)Definitely fail to reject the null hypothesis with either α = .05 or with α = .01

Question

Quizplus · Accepted Answer

Switching from a one-tailed to a two-tailed test means that the rejection region is now in both tails of the distribution instead of just one. This means that the critical values for the test will be different, making it possible for the result to fall within the non-rejection region. Therefore, it is possible that the null hypothesis could be rejected with α = .05 in the one-tailed test, but not in the two-tailed test. It is not possible to determine whether the null hypothesis would be rejected or not without more information about the sample and effect size.

A Researcher Evaluates a Treatment Effect Using a One-Tailed Hypothesis