Question 7.21

7.21 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 a lot shorter to a lot longer. The sample mean was −0.55, and the sample standard deviation was 2.16.

  1. These data are integer values. Do you think we can still use the -based methods of this section? Explain your answer.
  2. Is there evidence that the mean rating is different from zero? Carry out the significance test using and summarize the results.

7.21

(a) Because , we can still use the t procedure for non-Normal distributions. (b) . The data are significant at the 5% level; there is evidence that the mean rating is different from zero. (People do not feel that the trips take the same time.)