In Exercise 13.17, we considered a regression of y 5 oxygen consumption on x 5 time spent exercising.

Summary quantities given there yield n 5 20 x 5 2.50 Sxx 5 25 b 5 97.26 a 5 592.10 se 5 16.486

a. Calculate sa1b12.02, the estimated standard deviation of the statistic a 1 b(2.0).

b. Without any further calculation, what is sa1b(3.0) and what reasoning did you use to obtain it?

c. Calculate the estimated standard deviation of the statistic a 1 b(2.8).

d. For what value x* is the estimated standard deviation of a 1 bx* smallest, and why? x