What were Piliavin et al. (1969) unable to control in their field experiment investigating bystander behavior?
the specific size of the passenger cohort in the critical area
the timing of the model's intervention
the physical appearance and dress of the victim
the physical location where the victim collapsed
105 exam-style questions on OCR A Level Psychology Responses to people in need, covering Piliavin et al. (1969): Subway Samaritan and Levine et al. (2001): Cross-cultural altruism. Each one has a worked solution and a mark scheme showing where the marks go.