There are 4327 colleges in a certain country and the number full-time students is 13, 287,563.
(a) Are the numbers of full-time students at different colleges discrete or continuous? Explain your answer.
(b) What do you think is wrong with surveying college student by mailing questionnaires to 10,000 who are randomly selected?
(c) If we randomly select four colleges and survey all their full-time students, what type of sample is obtained? (random, systematic, convenience, stratified, cluster)