A TV station wishes to obtain information on the TV viewing habits in its market area. The market area contains one city of population 170,000, another city of 70,000, and four towns of about 5000 inhabitants each. The station suspects that the viewing habits may be different in larger and

smaller cities and in rural areas. Which of the following sampling designs would give the type of information that the station requires?

(a) A cluster sample using the cities and towns as clusters

(b) A convenience sample from the market area

(c) A simple random sample from the whole market area

(d) A stratified sample from the cities and towns in the market area

(e) An online poll that invites all people from the cities and towns in the market area to participate

The population of three cities are 170,000, 70,000 and 5000 each.

The random assignment method assigns subjects to treatments based on chance. Before the treatments are applied, random assignment establishes treatment groups that are comparable (except for chance variance). In experiments, randomization and comparison combined prevent bias or systematic favoritism.

Each of the three cities has a population of $170,000,70,000,$ and $5000$ people. The station is skeptical that watching habits differ in urban and rural areas. Stratified random samples are samples taken from different strata in a diverse population using simple random sampling.

The sampling method stratified random sample should be used to collect the required information because samples from each area should be selected, and then all of the selected cities should be equally represented in the chosen sample. As a result, the best solution is (d).