The pollster tells us that when opinion researchers need a representative population sample, they choose their sample on the basis of national census data. Not everyone participates in the census, despite its being mandatory. If it became voluntary, the participation rate would go down, and national polls would have less accurate results.
Which of the following is a required assumption?
The goal of the poll is to get a representative data based on demographic characteristics of the population, but if the people who will stop participating in a voluntary census have the same demographic characteristics as the ones who currently refuse to participate in the mandatory one, then it would make no difference whether the census is voluntary or mandatory. Thus, for the argument to properly conclude that the results would be less accurate, the group of people who participate in a voluntary census must have different demographic characteristics than the group that participates in the mandatory one, as (C) correctly points out.
Does this make sense?
Let me know if you have any further questions.
MinervaAugust 30, 2019
This makes perfect sense, thanks @Irina!
RaviAugust 30, 2019
@Minerva, let us know if you have any other questions!
