Question

For a two-tailed test with variance unknown, n=19, and a=0.05, what is the critical value?

Answer 1

This corresponds to a two-tailed test, for which a t-test for one mean, with unknown population standard deviation, using the sample standard deviation, will be used.

Based on the information provided, the significance level is $\alpha = 0.05,$ $df=n-1=18$ and the critical value for a two-tailed test is $t_c = 2.100922.$