b) An engineer studying whether a downhill section of a highway needs to be widened, measures the speed of motorists traveling along the highway. A sample of 90 cars gives a mean speed of 110.2 km/h and a standard deviation of 6 km/h. Summary Output 3.1 and 3.2 was obtained Summary Output 3.1: One- Sample T Test of mu = 112 vs not= 112 N Mean StDev SE Mean 95% CI P 90 110 . 200 6.000 0. 632 (108. 943, 111 . 457) -2.85 0:005 Summary Output 3.2: One - Sample T Test of mu - 112 vs