Refer to Example 12.12 in which x test track speed and y rolling test speed.

a. Minitab gave and . Why is the former estimated standard deviation smaller than the latter one?

sbˆ

01bˆ

1 s (47) 5 .186 bˆ

01bˆ

1(45) 5 .120 S 5 0.0737573 R–Sq 5 80.2% R–Sq(adj) 5 78.4%

Fermi pos 5 0.7217 2 0.4327 n 5 10 a 5 .05

b. Use the Minitab output from the example to calculate a 95% CI for expected rolling speed when test speed 45.

c. Use the Minitab output to calculate a 95% PI for a single value of rolling speed when test speed = 47.