10.26 An independent-samples t test and getting people to turn off the light: Do you turn off the light when you leave the room? South Korean researchers wondered how they could increase the number of people who do (Ahn et al., 2014). They compared two poster campaigns. In one, an image of a light bulb was anthropomorphized by giving it eyes, nose, and a mouth, as well as adding the words, “I’m burning hot, turn me off when you leave!” (p. 225). In a second, there were no human features on the light bulb and the text simply said, “Our bulbs are burning hot, turn the lights off when you leave!” (p. 226). Participants were randomly assigned to view one of these posters and then were asked to rate a series of items about how likely they would be to behave in an environmentally friendly manner. The scale went from 1 (very unlikely) to 9 (very likely). The summary statistics for the data below approximate the actual means and standard errors in the study.

Anthropomorphism Nonanthropomorphism 7.2 5.3 8.1 6.2 7.5 6.5 6.9 7.0 6.6 5.6 7.4 6.8 6.5 6.2

a. Conduct all six steps of an independent-samples t test. Be sure to label all six steps.

b. Report the statistics as you would in a journal article.

c. Is there a shortcut you could or did use to compute your hypothesis test? (Hint: There are equal numbers of participants in the two groups.)

d. Calculate the 95% confidence interval.

e. State in your own words what we learn from this confidence interval.

f. Explain why interval estimates are better than point estimates. g. Calculate the appropriate measure of effect size. h. Based on Cohen’s conventions, is this a small, medium, or large effect size? i. Why is it useful to have this information in addition to the results of a hypothesis test?