A random sample of 25 students taken from a university gave the variance of their GPAs equal to .19.
a. Construct the 99% confidence intervals for the population variance and standard deviation. Assume that the GPAs of all students at this university are (approximately) normally distributed.
b. The variance of GPAs of all students at this university was .13 two years ago. Test at a 1% significance level whether the variance of current GPAs at this university is different from .13.