Consider the data and simple linear regression in Exercise 6-1.

(a) Find the mean thermal conductivity given that the product density is 0.2350.

(b) Compute a 95% CI on this mean response.

(c) Compute a 95% PI on a future observation when product density is equal to 0.2350.

(d) What do you notice about the relative size of these two intervals? Which is wider and why?