A two-tailed hypothesis test is being used to evaluate a treatment effect with α = .05.If the sample data produce a z-score of z = -2.24,what is the correct decision?
A)Reject the null hypothesis and conclude that the treatment has no effect
B)Reject the null hypothesis and conclude that the treatment has an effect
C)Fail to reject the null hypothesis and conclude that the treatment has no effect
D)Fail to reject the null hypothesis and conclude that the treatment has an effect

Question

Quizplus · Accepted Answer

Since this is a two-tailed hypothesis test, the rejection region exists in both tails of the distribution, with a total area of α/2 = .025 in each tail. A z-score of -2.24 corresponds to a probability of .0127 in the left tail of the distribution, which is smaller than α/2. Therefore, we reject the null hypothesis and conclude that the treatment has an effect.

A Two-Tailed Hypothesis Test Is Being Used to Evaluate a Treatment