A large medical professional organization with membership consisting of doctors, nurses, and other medical employees wanted to know how its members felt about HMOs (health maintenance organizations). Name the type of sampling plan they used in each of the following scenarios:
a. They randomly selected 500 members from each of the lists of all doctors, all nurses, and all other employees and surveyed those 1500 members.
b. They randomly selected ten cities from all cities in which the members lived, and then surveyed all members in those cities.
c. They randomly chose a starting point from the first 50 names in an alphabetical list of members, and then chose every 50th member in the list starting at that point.