Question: An experiment is performed to study the effects of movie depiction of altruism on expressed attitudes toward helping. Each member of 12 pairs of identical twins is randomly assigned to one of two treatment conditions. One member of each pair watches scenes from a movie showing altruistic behavior and self-sacrifice. The other member watches neutral scenes from the same movie. Each participant is then given a self-rating scale designed to elicit attitudes about helping behavior. High scores represent a low threshold for the expression of helping. The results are as follows:

Test the null hypothesis.