If we are using a nondirectional alternative hypothesis for a z-test with α = .05, what critical value(s) should be used for rejecting the null hypothesis?
A) -1.96 only or +1.96 only.
B) +1.65 only or -1.65 only.
C) either ±1.96
D) either ±1.65

Question

Quizplus · Accepted Answer

When using a nondirectional alternative hypothesis with α = .05, we must split α/2 between the two tails of the distribution. This means that each tail has an α/2 = .025 probability of occurring. Looking up the corresponding z-scores in a z-table gives us ±1.96 as the critical values. Thus, either ±1.96 can be used for rejecting the null hypothesis.

If We Are Using a Nondirectional Alternative Hypothesis for a Z-Test