12.26 The following are results from a regression model analysis:

yn = -9.50 + 17.8x1 17.12

+ 26.9x2 113.72

- 9.2x3 13.82 R2 = 0.71 n = 39 The numbers in parentheses under the coefficients are the estimated coefficient standard errors.

a. Compute two-sided 95% confidence intervals for the three regression slope coefficients.

b. For each of the slope coefficients test the hypothesis H0 : bj = 0 Application Exercises