10.21 [EX10-021] Two men, A and B, who usually commute to work together, decide to conduct an experiment to see whether one route is faster than the other. The men believe that their driving habits are approximately the same, and therefore they decide on the following procedure. Each morning for 2 weeks, A will drive to work on one route and B will use the other route. On the first morning, A will toss a coin. If heads appear, he will use route I; if tails appear, he will use route II. On the second morning, B will toss the coin: heads, route I; tails, route II. The times, recorded to the nearest minute, are shown in the following table.

Assume commute times are normal and estimate the population mean difference with a 95% confidence interval.

Day Route M Tu W Th F M Tu W Th F I 29 26 25 25 25 24 26 26 30 31 II 25 26 25 25 24 23 27 25 29 30