Cooling Down. Cooling down with a cold drink before exercise in the heat is believed to help an athlete perform. Researcher J. Dugas explored the difference between cooling down with an ice slurry (slushy) and with cold water in the article “Ice Slurry Ingestion Increases Running Time in the Heat” (Clinical Journal of Sports Medicine, Vol. 21, No. 6, pp. 541–542). Ten male participants drank a flavored ice slurry and ran on a treadmill in a controlled hot and humid environment. Days later, the same participants drank cold water and ran on a treadmill in the same hot and humid environment. The following table shows the times, in minutes, it took to fatigue on the treadmill for both the ice slurry and the cold water.

Subject Cold Water Ice Slurry 1 52 56 2 37 43 3 44 52 4 51 58 5 34 38 6 38 45 7 41 45 8 50 58 9 29 34 10 38 44 At the 1% significance level, do the data provide sufficient evidence to conclude that, on average, cold water is less effective than ice slurry for optimizing athletic performance in the heat? (Note: The mean and standard deviation of the paired differences are −5.9 minutes and 1.60 minutes, respectively.)

In Exercises 10.161–10.166, apply Procedure 10.7 on page 513 to obtain the required confidence interval. Interpret your result in each case.