A two-tailed test is _______ powerful than a one-tailed test if we are sure the difference is in the direction that we would have predicted.
A) more
B) less
C) equally
D) We cannot tell.

Question

Quizplus · Accepted Answer

In a two-tailed test, the rejection region is split between both tails. Therefore, when we predict a specific direction and perform a two-tailed test, the rejection region is farther away from the mean, resulting in less power to reject the null hypothesis. So, a one-tailed test is more powerful than a two-tailed test when we are sure of the direction.

A Two-Tailed Test Is _______ Powerful Than a One-Tailed Test