Kyle believes that exposure to violence, even pretend violence, contributes to increased aggression in children. Specifically, he thinks that children who play a lot of violent video games will tend to be more aggressive than children who do not play violent video games. In his study, for each child, he is tracking the number of hours spent playing video games and counting the number of aggressive acts each day, and he will look at the relationship between these two variables. This study is the test of his