Will Byers wants to buy a new computer to spy on Russians with, but needs a very good one. There is a computer company that claims that one of their models will get a 3DMark performance test score of 20000 (or greater). He buys a sample of 8 computers and got the following scores: 19883, 19825, 19938, 20008, 19984, 20044, 19807, 19869. Assume that the scores are normally distributed.

(a) Construct a 90% Confidence Interval Upper Bound for the population standard deviation of all of these scores, .

(b) Construct a 90% 2-sided Confidence Interval for the population standard deviation of all of these scores, .