Refer to the previous exercise.

a. Find the margin of error for constructing a 95% confidence interval for the difference between any pair of the true means. Interpret by showing which pairs of bumpers (if any) are significantly different in their true mean repair costs.
b. For Tukey 95% multiple comparison confidence intervals, the margin of error is 8.4. Explain the difference between confidence intervals formed with this method and separate confidence intervals formed with the method in part a.
c. Set up indicator variables for a multiple regression model including bumper type.
d. The prediction equation for part c is = 13 - 11x1 - 10x2. Explain how to interpret the three parameter estimates in this model, and show how these estimates relate to the sample means for the three bumpers.

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Bumper A Bumper IB 2 Bumper C 15 Source Bumper Error Total DF MS 148.00 74.00 4.00 18.50 0.021 12.00 160.00