A researcher conducts an experiment in which half of the participants read a story designed to reduce prejudice (story group), whereas the other half of the participants read material unrelated to prejudice (control group). After reading the material, half of the participants describe a minority group while alone, and the other half describes the minority while in a peer group. The dependent variable is the number of positive statements made about the minority group. The mean number of positive statements in the four conditions were: Although the final conclusions would be based on statistical significance tests, these results indicate a(n)