Aresearcher conducts an experiment in which half of the number of participants read a story designed to reduce prejudice (story group), whereas the other half 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 a minority group in the presence of their peers. the dependent variable is the number of positive statements made about the minority group. the mean number of positive statements in the four conditions was: picture although the final conclusions would be based on statistical significance tests, these results indicate a(n)