Confidence Intervals for Regression Coefficients A confidence interval for the regression coefficient b1 is expressed as b1 - E 6 b1 6 b1 + E where E = ta>2sb1 The critical t score is found using n - (k + 1) degrees of freedom, where k, n, and sb1 are described in Exercise 17.

Using the sample data from Example 1, n = 153 and k = 2, so df = 150 and the critical t scores are {1.976 for a 95% confidence level. Use the sample data for Example 1, the Statdisk display in Example 1 on page 483, and the StatCrunch display in Exercise 17 to construct 95% confidence interval estimates of b1 (the coefficient for the variable representing height)

and b2 (the coefficient for the variable representing waist circumference). Does either confidence interval include 0, suggesting that the variable be eliminated from the regression equation?