14.15 Tukey holding time comparisons Refer to the previous exercise. We could instead use the Tukey method to construct multiple comparison confidence intervals. The Tukey confidence intervals having overall confidence level 95% have margins of error of 5.7, compared to 4.7 for the separate 95% confidence intervals in the previous exercise.

a. According to this method, which groups are significantly different?

b. Why are the margins of error larger than with the separate 95% intervals?