b) An engineer studying whether a downhill section of a highway needs to be widened, measures the speed of motorists travelling 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 T 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