24. Appendix B Data Set: Old Faithful Refer to Data Set 11 in Appendix B and use the time intervals before and after each eruption.

a. Using a 0.05 significance level, test the claim that the before>after differences have a mean equal to 0. What does the result suggest about the timing of eruptions?

b. Construct a 95% confidence interval estimate of the mean difference between the times before eruptions and the times after eruptions.

9-4 BEYOND THE BASICS