Question

Which of the following is a benefit to using a one-tailed t-test (as opposed to a two-tailed test)?

A) It improves the predictive power of the independent samples t-test.

B) It reduces the impact of within-groups variance.

C) We are more likely to reject the null hypothesis when the null hypothesis is false.

D) We are less likely to reject the null hypothesis when the null hypothesis is false.

Answer 1

In the one tailed test we are testing

or

hence if we reject the null hypothesis we have a clear idea about the result of the test

while in two tailed test we are testing

so if we reject the null hypothesis the result is 50:50 it can go either in two directions

so we can say that e are more likely to reject the null hypothesis when the null hypothesis is false.