I can't figure this one out

You think all professors are uncoordinated, but then you see your social psychology professor make a diving catch down the left-field line at an intramural softball game against the arts department team. you also notice that your professor hits lead-off for the team and is able to score from second base on a ground-out. you maintain your original stereotype of professors as uncoordinated by deciding that this one individual is an exception to the rule because he is a “young professor.” this is an example of

Which statement defines personality

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