3. In order to derive a confidence interval of the population variance, a random sample of n observations is drawn from a normal population. Use this information to find χ2α/2,df and χ21 − α/2,df under the following scenarios.

a. A 95% confidence level with n = 18.

b. A 95% confidence level with n = 30.

c. A 99% confidence level with n = 18.

d. A 99% confidence level with n = 30.