Consider the data in Exercise 4-17 on the time (in minutes) to process hot-rolled steel for a

Question:

Consider the data in Exercise 4-17 on the time (in minutes) to process hot-rolled steel for a sample of size 10.
(a) Find a 98% confidence interval for the mean time to process hot-rolled steel. What assumptions do you have to make to solve this problem?
(b) Find a 95% confidence interval for the variance.
(c) Test the hypothesis that the process variability, as measured by the variance, exceeds 0.80. Use α = 0.05.