The sampling examples below use either the stratified or the cluster method of sampling. Select the examples that use the strati
fied method. A city council wants to know if elementary students in its city are meeting national standards. Eight schools are selected from the city's 30 total elementary schools, and the test scores of all students in the selected schools are evaluated. □ A landlord wants to know the average income of his tenants. He selects three of his eight apartment complexes and collects income information from several randomly chosen tenants within the selected complexes. A questionnaire is created to gauge studert opinion on a new university cafeteria. A sample of 40 eshmen. 50 sophomores, 60 juniors, and 50 seniors is selected to fill out the questionnaire. A health agency needs to assess the performance of hospitals in a region but does not have the resources to evaluate each hospital. To reduce costs, the agency selects 5 of the 23 hospitals in the region and samples data related to performance from randomly chosen days and times. □ A potato field is believed to be infected with a plant disease. The field is divided into 10 equal areas, and 25 potatoes are selected from each area to be tested for the disease.
Answer: The examples that use the stratified method are: (1). A questionnaire is created to gauge student opinion on a new university cafeteria. A sample of 40 eshmen, 50 sophomores, 60 juniors, and 50 seniors is selected to fill out the questionnaire. (2). A potato field is believed to be infected with a plant disease. The field is divided into 10 equal areas, and 25 potatoes are selected from each area to be tested for the disease.
Step-by-step explanation: Stratified sampling technique is a type of sampling where the population under study has a number of distinct categories or sub-groups in which it is divided into. These categories or sub-groups are called strata and are defined by certain characteristics related to the variable or particular finding under interest. The sampling frame can be organized into separate mutually exclusive strata and then each ‘stratum’ is being sampled as an independent sub-population out of which individual elements can be randomly selected. In this case, each unit in a stratum, that is, each element in a group has a chance of being selected. With stratified sampling, the best result occurs when elements within strata are internally homogenous.
