Question

A study of the effects of television violence on children was conducted at a local elementary school. children were randomly selected from the fourth grade and shown a ten-minute cartoon with violent content. the children were then sent to the playground with other children. children who were shown the cartoon displayed more aggression in their play than the children who did not see the cartoon. these findings supported the researchers' hypothesis that viewing television violence causes aggressive behavior. the selection of subjects for this study makes it likely that the researcher's conclusion about the hypothesis has:

Answer 1

I believe the answer is Causal or internal validity
Causal or internal validity is a form of research method that being done in order to obtain truth about a certain cause-effect relationship.
This method is carried out by Comparing the initial cause-effect with additional  Alternative cause and see whether the effect is changing.