: A car manufacturer asserts that with the new collapsible bumper system, the mean body repair cost for the damage sustained in a collision impact of 15 miles per hour does not exceed $400. To test the validity of this claim, 6 cars are crashed into a barrier at 15 miles per hour and their repair costs recorded. The mean and standard deviation are found to be $458 and $48, respectively. At the = .05 signicance level, does the test data contradict the manufacturer's claim that the repair cost does not exceed $400? You may assume the sample was taken from a normal population.