Confidence Interval for a Regression Coefficient 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 as described in Exercise 17.

Use the sample data in Table 4 and the Excel display in Example 1 to construct 95% confidence interval estimates of b1 (the coefficient for the variable representing height of the mother) and b2 (the coefficient for the variable representing height of the father). Does either confidence interval include 0, suggesting that the variable be eliminated from the regression equation?