Question 8.16: Find a 95% confidence interval for the coefficient of Speed ......

ISE Principles of Statistics for Engineers and Scientists [987713]

Find a 95% confidence interval for the coefficient of Speed in the multiple regression model.

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From the output, the estimated coefficient is −1.8245, with a standard deviation of 0.2376. To find a confidence interval, we use the Student’s t distribution with 19 de-grees of freedom. The degrees of freedom for the t statistic is equal to the degrees of freedom for error. The t value for a 95% confidence interval is $t_{19, .025} = 2.093$ . The 95% confidence interval is

−1.8245 ± (2.093)(0.2376) = −1.8245 ± 0.4973 = (−2.3218, −1.3272)

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