Hazing within college fraternities is a continuing concern. Before a national meeting of college presidents, a polling organization is retained to conduct a survey among fraternities on college campuses, gathering information on hazing for the meeting. The investigators from the polling organization realize that it is not possible to find a reliable sampling frame of all fraternities. Using a list of all college institutions, they randomly sample 30 of them and then interview the officers of each fraternity at each of these institutions that has fraternities. Would you describe this as a simple random sample, cluster random sample, or stratified random sample of the fraternities? Explain.