Dr. Safe is curious as to whether exposing people to violent video games causes them to be more aggressive. He assigns half of his participants to play a violent video game for 5 minutes and the other half to play the same game for 25 minutes. Afterward, he has them play a board game and has a well-trained coder determine whether they are (3) very aggressive in their playing style, (2) barely aggressive, or (1) not at all aggressive. He finds that most of his participants, regardless of group assignment, are rated as (3) very aggressive. This outcome would be known as a(n):
