Aron and colleagues (1997) placed strangers in pairs and asked them to talk together following a series of instructions designed to help them become close. At the end of 45 minutes, individuals privately answered some questions about how close they now felt to their partners. (The researchers combined the answers into a "closeness composite.") One key question was whether closeness would be affected by either
(a) Matching strangers based on their attitude agreement
(b) Leading participants to believe that they had been put together with someone who would like them. The result for both agreement and expecting to be liked was that "there was no significant differences on the closeness composite". The researchers went on to argue that the results suggested that there was little true effect of these variables on closeness:
There was about 90% power in this study of achieving significant effects . . . for the two manipulated variables if in fact there were a large effect of this kind (d = .8). Indeed, the power is about 90% for finding at least a nearsignificant medium-sized effect (d = .5). Thus, it seems unlikely that we would have obtained the present results if in fact there is more than a small effect . . . .
Explain this result to a person who understands hypothesis testing but has never learned about power or effect size.