Compute the 90% confidence interval estimate of the population variance. A confidence interval for the population variance of will have the following form where n is the sample Imple 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)52 5 02 - (n - 1)52 X a/ 2 X 1 - a/2 Recall that the value of alpha is found by setting the confidence level equal to (1 - () and solving for @. 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 =