A School Counselor Was Concerned with the Rising Level of Violence

A school counselor was concerned with the rising level of violence at the school in which she was employed so she decided to try an experimental program to reduce the level of violence. She identified two groups of violent children at her school and randomly assigned them to two groups. Both groups of children are taught effective methods of dealing with other children and with frustration, but one group is reinforced every time they use any of these techniques and isolated when they are violent. The other group is isolated and punished in the form of having to do additional duties such as cleaning the bathrooms whenever they act violently. Some of the participants in both groups fail to complete the study but most of the ones that drop out are in the punishment group. The study found that both groups reduced their violent behavior by equal amounts. Which is the best conclusion to draw from this study?

A) There is no difference in the effectiveness of reinforcement versus punishment
B) The study is confounded by differential attrition and this might explain the failure to find any group differences
C) The study is confounded by a history bias and this might explain the failure to find any group differences
D) Reinforcement would have been demonstrated to be more effective if the study had lasted longer