Question

the

Answer 1

Sorry for my bad in previous reply. Please find corrected solution below.

From the previous part of this question the r.m.s error of the regression line was found to be 0.4176 inch.
Since the scatter diagram is football-shaped the r.m.s error of the regression line can be used like a standard deviation for the regression line. From a standard normal distribution table the values of z corresponding to 50% of the area under the normal distribution are z = -0.674 and z = 0.674. These values convert to -0.28 inch and 0.28 inch.