Consider the data in Exercise 1 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 ˆ 0.05.

Exercise
The following times(in minutes) to process hot-rolled steel are observed for a random sample of size 10:

5.4   6.2   7.9   4.8   7.5
6.2   5.5   4.5   7.2   6.2

(a) Find the mean, median, and mode of the processing times. Interpret the differences between them.

(b) Compute the range, variance, and standard deviation of the processing times and interpret them.