Chapter 12, Problem 6E

(a)

To determine

To explain what kind of survey design are they using.

Answer to Problem 6E

They are using the stratified sampling design.

Explanation of Solution

It is given in the question that at its website Gallup world poll describes their methods and they have explained through the report their methods. Thus, by looking at the report and the study conducted we can say that Gallup world poll is using the stratified sampling design because in this sample each country is a stratum, that is used by them in the survey.

(b)

To determine

To explain how does this affect the precision of its estimate for these countries.

Explanation of Solution

It is given in the question that at its website Gallup world poll describes their methods and they have explained through the report their methods. Thus, by looking at the report and the study conducted we can say that this affect the precision of its estimate for these countries as since the sample size of each country is (approximately) the same and the population of each country is in the millions, the precision of its estimates won't be affected or compromised. Remember that the fraction of population we've sampled doesn’t matter; it’s the sample size itself that’s important.