(a) Compute the 90% confidence interval estimate of the population variance. A confidence interval for the population variance ofwill have the following form where n is the sample size and s is the sample variance. The y values correspond to a chi-square distribution with n - 1 degrees of freedom where - and 1 - - are the upper tail areas. (n - 1)s2 (n - 1)s2 X a / 2 X 1 - a /2 Recall that the value of alpha is found by setting the confidence level equal to (1 - a) and solving for a. A 90% confidence interval is to be found. Expressing 90% as a probability gives 0.90, so we have 1 - a = 0.90. Therefore, a = 0.10, so _ and 1 - a The sample size is n = 20, so the degrees of freedom is n - 1 =