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#47239
Please post your questions below!
 plshelp
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#50424
Hi, could you please help explain why C is right and how to approach this problem. I know its a necessary assumption question. I didn't understand the connection between a lower participation rate and less accuracy if participation was voluntary. I assumed that the author was saying that the reason for less accuracy was that there would be less of a sample size and I took that for granted. I then went through the answer choices without a prephrase. I was attracted to answer choices that spelled out more about the assumption that if it were voluntary less people would participate and I narrowed it down to B and E. B seemed to be saying that no new people would be participating if it were voluntary which would confirm the premise that participation would be lower and E seemed to support the premise that participation would be lower because it would support the fact that participation in the mandatory census always would be greater. Is the issue that because the sample size is always just a proportional representation that I shouldn't have focused on numbers as the reason for the lack of accuracy? Or that I shouldn't have focused on supporting the premise that the participation rate would be lower because that is a premise I should just necessary assume is true because its a premise? Can you help me figure out what a better way to approach this question would have been?
 James Finch
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#50435
Hi Pls Help,

It sounds like you took a scattershot approach to the question, which tends to lead to the kind of confusion you described. This is an assumption question, so we always need to see whether there is a logical gap between a new element in the conclusion (ie something not in the premises but found only in the conclusion) and the premises; if there is, it's a Supporter type and our answer choice should fill the gap. If not, we have a Defender type that is much harder to prephrase. In this case, we can see that from the two conditionals given:

The premise: If census participation became voluntary, the participation rate would be much lower, or:

CPV :arrow: PR Down

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

CPV :arrow: LAROP

The obvious way to tie the two together is by saying that whenever participation rate goes down, the polls are less accurate because the lower participation rate doesn't reflect true demographics as well as the results from a mandatory census. So that's the prephrase I would use to answer this question. Let's look at the answer choices:

(A): Out of scope, as we're not concerned with making a census the only way to get accurate demographic data, but with tying a voluntary census to being less accurate.

(B): Possibly appealing on first read, but in fact deals with irrelevant information. People who don't currently participate in the census still not participating if it's voluntary doesn't serve to make a voluntary census less accurate.

(C): Deals with distinguishing voluntary and mandatory censuses, which is the scope we are looking for. Contender.

(D): Irrelevant, we don't care about people who don't participate in opinion polls.

(E): Doesn't deal with what happens in a voluntary census, so it doesn't help us.

So we're left with only (C) by process of elimination, but we can still show it to be correct. Using the Assumption Negation technique, we can see that:

The group of people who would participate in a voluntary national census would not differ in its demographic characteristics from the group of people who would participate in a mandatory national census

:arrow:

Polls designed to discover the opinions of the national population would not have less accurate results

This works perfectly with the premises in the stimulus, showing it to be the correct answer.

Hope this helps!
 dlehr99
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#72799
James Finch wrote:
So we're left with only (C) by process of elimination, but we can still show it to be correct. Using the Assumption Negation technique, we can see that:

The group of people who would participate in a voluntary national census would not differ in its demographic characteristics from the group of people who would participate in a mandatory national census

:arrow:

Polls designed to discover the opinions of the national population would not have less accurate results

This works perfectly with the premises in the stimulus, showing it to be the correct answer.

Hope this helps!
Can you help me understand the application of this negation technique? I would logically agree with the answer choice negation:
James Finch wrote:The group of people who would participate in a voluntary national census would not differ in its demographic characteristics from the group of people who would participate in a mandatory national census
But in the explanation provided the stimulus was also negated.
James Finch wrote:Polls designed to discover the opinions of the national population would not have less accurate results
Is this just to show the effect of the answer choice negation on the stimulus, as I don't think the technique calls for negating the stimulus. Either way, I'm hung up on how the newly negated answer choice of --voluntary participants not differing in demographic characteristics -- weakens the argument. My thought process is: Okay it doesn't change. That seems like a neutral effect on the accuracy of the results not that they would be less accurate.

AND now I'm realizing that's exactly the point being made above... jeesh :roll: . It weakens it because it doesn't agree with the Pollster's comment that there would be less accurate results.

Posting this anyway so an expert can confirm and because I think this might be helpful to others.
 Paul Marsh
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#72858
Hi dlehr99! You are right on the money - the negation of Answer Choice (C) weakens the argument because if the demographics are the same, we would expect the accuracy of the polls to be about the same (and therefore the Pollster's conclusion wouldn't make any sense). Nice job working through that! The Assumption Negation technique is a very helpful tool but it can be a bit confusing at first - give it plenty of practice and you'll be able to apply it without tripping yourself up.

As for your first question - when James wrote,
James Finch wrote: Polls designed to discover the opinions of the national population would not have less accurate results
That was just his way of showing the effect of negating the answer choice! Remember that when we use the Assumption Negation technique, all we do is negate the answer choice in question and then plug it in to the argument. If it makes the argument fall apart, it's the right answer! James was demonstrating that when we plug the negation of Answer Choice (C) into the argument, the conclusion no longer really makes sense and the conclusion becomes false.

Hope that helps!
 dlehr99
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#72895
Thanks a lot, and I appreciate you confirming!

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