4.The mean throwing distance of a football for Marco, a high school freshman quarterback, is 40 yards, with a standard deviation of two yards. The team coach tells Marco to adjust his grip to get more distance. The coach records the distances for 20 throws. For the 20 throws, Marco's mean distance was 45 yards. The coach thought the different grip helped Marco throw farther than 40 yards. Assume the throw distances for footballs are normal.

a)Use the critical value approach to conduct a hypothesis test using a preset= 0.05.

b)Use the -value approach to conduct a hypothesis test using a preset= 0.05.