give the critical value(s) of:

1. A left-tailed test with alpha = 0.10, unknown sigma, and a sample of size 23

Mr F says: Use the t-distribution. All you need is here: http://www.itl.nist.gov/div898/handbook/eda/section3/eda3672.htm
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.

Mr F says: Not quite sure what you want here. Note that df = 16 - 1 = 15 and Pr(t < -1.443) = 0.0848.
I'm stuck on these three. I'm pretty sure number 2 is +/- 1.645

Mr F says: Correct.
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