In Bandura et al.'s (1961) study on the transmission of aggression, how did the researchers control for the potential confounding variable of the children's pre-existing levels of aggression?
By having a nursery school teacher and an experimenter rate each child's aggression on four 555-point scales, then matching the children in triplets before allocating them to conditions.
By administering a standardized pictorial self-report questionnaire to the children to measure baseline levels before random allocation.
By selecting only children who scored within the average range on parent-completed child behaviour checklists, excluding highly aggressive children.
By conducting a baseline observation of free play and allocating children to groups based on their preference for aggressive toys.
