the highway department wanted to determine if people on a certain stretch of highway were driving at the posted speed limit of 65 mph or not. they set up a system to sample the drivers at different times of day and found the average speed of 100 drivers in the stretch was 62.4 mph with a standard deviation of 18.1 mph. the critical value for an alpha level of 0.05 will be 1.98 for this test. calculate the test statistic for this test and report to two decimal places.