In their classic study on bystander behavior (the 'Subway Samaritan' study), Piliavin et al. (1969) gathered data from an estimated 4,450 4,450\,4,450 passengers on the New York subway. Which of the following statements correctly identifies both the sampling technique used to obtain these participants and the demographic composition of the sample?
An opportunity sample, with approximately 55%55\%55% white and 45%45\%45% black passengers.
A volunteer sample, with approximately 55%55\%55% white and 45%45\%45% black passengers.
A random sample, with approximately 50%50\%50% white and 50%50\%50% black passengers.
An opportunity sample, with approximately 75%75\%75% white and 25%25\%25% black passengers.
