MATH- STATISTICS

Multistage health survey A researcher wants to study
regional differences in dental care. He takes a multistage
sample by dividing the United States into four regions,
taking a simple random sample of ten schools in each
region, randomly sampling three classrooms in each
school, and interviewing all students in those classrooms
about whether they’ve been to a dentist in the previous
year. Identify each stage of this sampling design, indicating
whether it involves stratification or clustering.