:12b. Solution. 71 inches is (71 - 68)/3 = 1 SD above
average. So sample persons 71 inches tall have an average weight
0.6 x 1 = .6 SD's above average, that is, 120 + (.6 x 20) = 132
pounds. The SD of the weights of these people is the rms average
deviation from the regression line, or 16 pounds. Thus the
percentage of those who weigh between 116 and 148 pounds is the
area under the normal curve between -1 and 1, or 68%.