In Bandura et al.'s (1961) study on the transmission of aggression, how did the researchers control for the children's pre-existing levels of aggression to ensure well-matched groups?
By assessing the children's behavioral responses to a structured laboratory-based frustration task prior to the main experiment.
By having a nursery teacher and the experimenter rate each child on four 555-point scales of aggressive behavior.
By administering a standardized personality questionnaire to the children's parents regarding aggression at home.
By using a double-blind random allocation procedure without any pre-experimental behavioral assessment.