If you have a two-tailed test with an alpha (alpha) is 0.01, what is the critical value?

Question

If you have a two-tailed test with an alpha is 0.01, what is the critical value? Show your work.

Answer 1

Since it is a two-tailed test the critical values correspond to alpha/2 = 0.005.

For a t-test that would be the +/- the t-score for 0.005 tail value at determined degrees of freedom.

For a z-test (population standard deviation known and sample size >= 30), then that would be +/- the z-score for a 0.005 tail value, which would be the z-score associated with a probability of 0.995 = 2.58