Consider the regression on the Census data presented in section 7.6.

(a) Section 7.6 gives the value of SD

(b) for this regression. The value of s is 43,427. Use equation (7.5) to figure out what Σi= −

n i x x 1

( )2 must be.

(b) The value of a for this regression is −17,136. What is ˆy0 if x0 = 4?

(c) The average value for years of schooling in these data is 12.43. In exercise 7.11, we proved that

Using this information and the answer to part

a, what is the variance of ˆy0 if x0 = 4? What is the 95% confidence interval for this predicted value?

(d) Answer parts b and c again under the assumption that x0 = 13.

(e) Answer parts b and c again under the assumption that x0 = 23.

1 V()=0 + (x-x) n +. n (*=*) i=1