The return-trip effect. We often feel that the return trip from a destination takes less time than the trip to the destination even though the distance traveled is usually identical. To better understand this effect, a group of researchers ran a series of experiments.9 In one experiment, they surveyed 69 participants who had just returned from a day trip by bus. Each was asked to rate how long the return trip had taken, compared with the initial trip, on an 11-point scale from 25 = a lot shorter to 5 = a lot longer. The sample mean was 20.55, and the sample standard deviation was 2.16.

(a) These data are integer values. Do you think we can still use the t-based methods of this section? Explain your answer.

(b) Is there evidence that the mean rating is different from zero? Carry out the significance test using  5 0.05 and summarize the results.