The plan is to collect samples from 450 households. Imagine that a friend hears this figure and expresses skepticism--"how can 450 be enough to generalize to the population of Atlanta?"

1. Explain to your friend why a random sample--even if it has "only" 450 households--can generalize to the population.

2. Why would it be important to conduct antibody tests on a random sample of people from the Atlanta area?

3. What are some ways the CDC might conduct this random sample? See Hints A & B

A. How might they obtain a simple random sample of Atlanta residents? How might they obtain a cluster sample? (What could they use as clusters?)

B. How might they conduct a stratified random sample? (Imagine that they want to use neighborhoods/zip codes as the strata.)

***After conducting the antibody study on a random sample of Atlanta residents, the CDC will have an estimate of the rate of infection in the sample.

4. To whom will they be able to generalize this rate of infection--that is, to which population of interest?

5. What might happen if some of the randomly sampled people in Atlanta refuse to have their blood drawn for this CDC study?

6. Will that affect the sample's generalizability? Why or why not?

7. Which big validity is this example concerning?