Confidence Interval Estimate of the Slope (β1)

You can also test the existence of a linear relationship between the variables by calculating a confidence interval estimate of β1 and determining whether the hypothesized value (β1 = 0) is included in the interval.

You calculate the confidence interval estimate of β1 by multiplying the t statistic by the standard error of the slope, and then adding and subtracting this product to the sample slope:

Sample slope ± t statistic (standard error of the slope) (9.15)

For the moving company data, using the Minitab and JMP regression results in Figures 9.5 and 9.6 on page 217, you calculate the lower and upper limits of the confidence interval estimate for the slope of cubic footage and labor hours as follows: ...

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