Derek, a neuropsychology graduate student, works in a behavioral eating research lab. derek suggests to the lead investigator that injecting people with leptin will them lose weight. his idea is quickly shot down by a classmate, who states, "not so fast, derek; "

Donald is studying the eating habits of all students attending his school. he samples the population by dividing the students into groups by grade level and randomly selecting a proportionate number of students from each group. he then collects data from the sample. which type of sampling is used? select the correct answer below: systematic sampling convenience sampling stratified sampling cluster sampling