Answer
The critical value is -1.327. The rejection region is every value below -1.327.
Work Step by Step
Using TI-84 calculator:
1. 2nd
2. VARS
3. Scroll down to invT
4. Input alpha given in the problem for the area. In this case area = 0.1.
5. Input n -1 for degree of freedom. In this case, df = 19.
6. The output is the critical value and the rejection region.
