12.24 The following are results from a regression model analysis:

yn = -3.54 + 7.4x1 11.82

+ 3.2x2 11.42

+ 10.1x3 14.32 R2 = 0.78 n = 41 The numbers below the coefficient estimates are the sample standard errors of the coefficient estimates.

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