Heika and lucille were both passed over for a promotion at work. heika is sure that the boss does not like him, but he believes that lucille was passed over because she is really a poor worker. his attribution of the cause of the event can be explained in terms of

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