# Question

Several retired bicycle racers are coaching a large group of young prospects. They randomly select seven of their riders to take part in a test of the effectiveness of a new dietary supplement that is supposed to increase strength and stamina. Each of the seven riders does a time trial on the same course. Then they all take the dietary supplement for 4 weeks. All other aspects of their training program remain as they were prior to the time trial. At the end of the 4 weeks, these riders do another time trial on the same course. The times (in minutes) recorded by each rider for these trials before and after the 4-week period are shown in the following table.

a. Construct a 99% confidence interval for the mean d of the population paired differences, where a paired difference is equal to the time taken before the dietary supplement minus the time taken after the dietary supplement.

b. Test at a 2.5% significance level whether taking this dietary supplement results in faster times in the time trials.

Assume that the population of paired differences is (approximately) normally distributed.

a. Construct a 99% confidence interval for the mean d of the population paired differences, where a paired difference is equal to the time taken before the dietary supplement minus the time taken after the dietary supplement.

b. Test at a 2.5% significance level whether taking this dietary supplement results in faster times in the time trials.

Assume that the population of paired differences is (approximately) normally distributed.

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