Consider table 12.8.

(a) Which estimate or estimates of b1 have confidence intervals that don’t contain the population value β1 = 4,000? How do we know?

(b) Which estimate or estimates of b2 incorrectly reject the null hypothesis H0 : β2 = 0 in favor of the alternative hypothesis H0 : β2 ≠ 0? Again, how do we know?

(c) Return to chapter 6. Ordinarily, with what frequency would we expect to incorrectly reject null hypotheses that are true?

(d) Considering parts a and

b, have we incorrectly rejected true null hypotheses with greater or less frequency than we might have expected? In either case, how could this happen?