a random sample of vehicles n=36 were selected and fitted with a new brake design a standardized braking test was then performed on all the vehicles and the stopping dsitances were recorded. the population stopping distance using this test is a mean of 65 feet with a standard deviation of 23 feet. you find that the mean stopping distance for your sample is 60 feet. your job is to determine if the new brake design significantly decreased the stopping distance of these vehicles at an alpha level of 0.05. compute the test statistic z test for the sample. what is the correct z score for the sample mean