polly thinks that her father and mother have been replaced by two people who are simply acting as her father and mother. she believes that someone found people who look exactly like her parents and exchanged them. polly's delusion is rare and is called

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