Which of the following was not a dependent variable measured by the observers in the Piliavin et al. (1969) Subway Samaritan study?
The time elapsed between the victim's collapse and the first passenger's offer of help
The total number of passengers who stepped forward to assist the victim
The self-reported level of emotional arousal of the bystanders obtained via post-trial interviews
The spontaneous verbal comments made by passengers in the subway carriage
