Logical Reasoning

PT150 · S3 · Q7 Pollster: When opinion researchers

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Pollster: When opinion researchers need a population sample that reflects the demographic characteristics of the national population, they choose their sample on the basis of national census data.

Conclusion (So)

If census participation became voluntary, polls designed to discover the opinions of the national population would have less accurate results.

Evidence

The accuracy of polling samples is based on census data.

If the census participation became voluntary, then even fewer people would participate in it.

Evaluate

In a straightforward Linking way, the author seems to be assuming, .

Why is that a dubious assumption? How could it be that fewer people participate in the census, but polls based on census data are just as accurate?

if the participation went down evenly across all demographic groups, then the census data would reflect the same relative composition of the country.

Take one small piece of census data: political party affiliation.

Say that every person in the country took the census and recorded their political party, and we found out it was like 35% Republican, 35% Democrat, 30% Independent.

Now say we removed 100,000 data points from the census. What would the political affiliation breakdown look like now?

We have no idea! It might look exactly the same. If you removed 35,000 Republican respondents, 35,000 Democrat ones, and 30,000 Independent ones, then the resulting pile of data points would still be 35/35/30.

Meanwhile, if we say , then that will skew the breakdown. It will look like there are more Independent voters than there really are, since they will now be over-represented relative to R's and D's.

Goal

The one objection that could tank this argument is if we said,

Thus, the argument must be assuming that the drop in participation for a voluntary census would not be the same across all demographic groups.

Which one of the following is an assumption on which the pollster's argument depends?

Using data from the national
Weakens, if anything
This makes it sound like pollsters have other ways to cross-reference the data they get from the census, which means a change to census participation might not really mess up the pollsters' samples. If we negate this and say, "using census data is the only way for pollsters to get a population sample", that would help the author argue that if we tinker with census data we might make population samples less accurate.
1% picked this
Among people who do not
Irrelevant Distinction
Would it hurt the argument if we negated this and said that there are tons of people currently abstaining from the mandatory census who would actually start doing the census if it were voluntary? No, that's weird but fine. The premise doesn't change — in the end the participation rate would be much lower. If that comes about because 1 million people who did the mandatory census won't do the voluntary whereas 500,000 people who didn't do the mandatory will do the voluntary, that doesn't change anything about the author's argument. In fact that weird flux where cooperators now abstain and abstainers now cooperate makes it more likely that the sample of people participating has meaningfully changed.
17% picked this
Correct
The group of people who
Why this is right
If we negate this, we get the objection we were predicting: the group of people who would participate in a voluntary census would not differ (would be identical, demographically, to the people who were participating in the mandatory one). If the mandatory census was 52% women, 48% men and the people who respond to the voluntary census are also 52% women, 48% men, then you're getting the same demographic profile of the country for that demographic characteristic. If this were the same for all demographic characteristics, then the census data between the mandatory and voluntary would be identical in terms of percent's, and that's all that matters when you're a pollster trying to construct a representative sample.
Skill tested: Necessary Assumption · how this choice captures the argument's function is the move to repeat next time.
73% picked this
The people who refuse to
Irrelevant Comparison
The author hasn't said or implied anything about the group of people who refuse to participate in opinion polls. He doesn't care whether their demographic characteristics are similar or different compared to any other group.
5% picked this
The percentage of the nation’s
Irrelevant Distinction
This has the tempting ruling out "not / no" form. When we negate this answer we get that "the percent of people participating in the mandatory national census does vary a lot from census to census", does that hurt the argument? Not really. The author is just saying that a voluntary census would have a much lower participation rate, which is compatible with ups and downs. If we saw the up and down of the participation rate of mandatory census on a line graph, the author is just saying that the participation rate of the voluntary census would be a line whose data points are lower than they would be if the census were mandatory. Perhaps an easier way to assess this is to ask yourself, "was the author assuming that participation in the mandatory census very, very consistent?" Nothing in the argument suggests that.
3% picked this

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