give the critical value(s) of:
1. A left-tailed test with alpha = 0.10, unknown sigma, and a sample of size 23
2. A two-tailed test with alpha = 0.10 a known value of sigma.
give the prob value(s) of:
3. A two-tailed test with t = -1.443 based on a sample of size 16.
I'm stuck on these three. I'm pretty sure number 2 is +/- 1.645 but not positive. Any help would be awesome!