What is different about the normality requirement for a confidence interval estimate of sigma and the normality requirement for a confidence interval estimate of mu?The normality requirement for a confidence interval estimate of sigma is ( less strict/ stricter) than the normality requirement for a confidence interval estimate of mu. Departures from normality have a (greater/ lesser) effect on confidence interval estimates of sigma than on confidence interval estimates of mu. That? is, a confidence interval estimate of sigma is (more/less)robust against a departure from normality than a confidence interval estimate of mu.