Thirty-five sophomores, 69 juniors and 24 seniors are randomly
selected from 461 sophomores, 328 juniors and 558 seniors at a
certain high school.

Every fifth teenager entering a concert is checked for
possession of drugs.

A researcher randomly selects an interviews fifty male and fifty
female teachers.

Based on 8000 responses from 32,500 questionnaires sent to its
alumni, a major university estimated that the annual salary of its
alumni was $103,000/year.

A community college student interviews everyone in a statistics
class to determine who owns a car.

To ensure customer satisfaction, every 5th phone call received
by customer service will be monitored.

The names of 70 contestants are written on 70 cards. The cards
are placed in a bag, and 3 names are picked from the bag.

A researcher for a publisher randomly selects 85 of the nation’s
middle schools and interviews all of the teachers at each of those
schools.

Simple Random Sample (SRS)

Systematic

Stratified

Convenience

Cluster