Question: what is the 95 confidence interval for the population variance?
Answer: For a 95% confidence interval, we have α=0.05, which gives 2.5% of the area at each end of the chi-square distribution. We find values of χ20.975=13.844 and χ20.025=41.923. Evaluating (n−1)s2χ2, we obtain 21.297 and 64.492.