In a recent poll, 71% of respondents reported that they cast votes in the most recent national election. Voting records show, however, that only 60% of eligible voters actually voted in that election.

Which of the following pieces of evidence, if true, would provide the best explanation for the apparent discrepancy?

A The margin of error for the survey was plus or minus five three percentage points.
B Fifteen percent of the survey's respondents were living overseas at the time of the election.
C Prior research has shown that that people who actually do vote are also more likely to respond to polls than those who do not vote.
D Many people who intend to vote are prevented from doing so by last-minute conflicts on election day or other complications.
E Some people confused the national election with other recent elections when responding to the poll.

I understood that question is asking to resolve the apparent discrepancy but do not find C too much convincing.
If people who gave vote are more interested to respond, the result must be accurate. How the result still daviates in that case? I never thought of C, rather I was tallying between B and D.
This is 31st question from CAT 3 test and this question is classified as weaken type. Is it weaken type?

I chose C between C and D.

Stem is about people who already cast vote, whereas D is about people who intend to vote and therefore is outside the scope.

ok so if voters who actually cast vote respond to the pole study, 71% response refer to the actual votes. Then why 60% votes are recorded? You mean that voters are dishonest?

i think C is correct because it explains that the survey results was over representative and hence actual voting was less than the survey predicted.

Dg_p has it. Because the group that responded to the survey was MORE LIKELY to have voted, this 71% is too high. Thus, it makes sense that a lower percentage actually voted.

I wouldn't really call this a "Weaken" question. In fact, there are "resolve a discrepancy" questions on this test.

I would say that the answer is a vehement (C). My reasons:

(a) The margin of error is not substantial enough to account for the 11% discrepancy.
(b) Citizens outside the territories are just as eligible to vote and thus, they would have cast their vote via mail.
(d) Even if the last minute glitch prevented many individuals from voting, the poll was conducted AFTER the voting process. Thus, those who had been eliminated or prevented from the voting process would have responded with a negative to the poll.
(e) There is no reason to assume that there were more than a single election being held.

Finally, why (c). Well the data suggesting that 60% of those eligible voted is accurate. It is not subject to sampling errors. However, the Poll's suggested numbers are contingent on the number of responders and how accurately the poll's sample space represents the actual sample space.

A bit like those notorious "Fox News Polls" that are often overwhelmingly conservative since they are not appropriately representative of the entire population. Just the loons.

Nice reasoning, Kapil.

Priyankur, I think you're misreading the question a bit. "60% of eligible voters voted" means that, of all of the people who were registered / allowed to vote, 60% of them voted. So if you have 100 people who are legally allowed to vote in the election 60 of them did.

The 71% refers to people who answered the poll, so you're talking about two different groups here. The poll surveyed a bunch of people (maybe by calling a random sample of local phone numbers?), some of whom did vote and some of whom did not vote. Some of the people polled may not even have been eligible to vote.

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Stacey Koprince
Instructor
Director of Online Community
ManhattanGMAT

Let me break this up....
suppose in a area 1000 ppl lived who were eligible to vote....
poll result shows 60% success... which means 600 ppl actually voted....

Now, the survey result-
71% said 'yes'.... the survey may have covered only 500 ppl or lets say the survey was responded by only 500 ppl who were excited about the election, though some of them would not have been able to vote...rest 500(including some of the ppl who actually voted) did not bother to answer the survey....

out of the 500 survey respondents, the number of ppl actually voted would be 355, rest would not have voted or were not eligible to vote...The agency which conducted the survey speculated and presented to the public that 71% voting has been done...

Hence, choice C fits the best...

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Thanks

thanks, addy..

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Tim Sanders
Manhattan GMAT Instructor

In a recent poll, 71% of respondents reported that they cast votes in the most recent national election. Voting records show, however, that only 60% of eligible voters actually voted in that election.

Which of the following pieces of evidence, if true, would provide the best explanation for the apparent discrepancy?

Question stem says- explain the discrepancy

What is the discrepancy?
71% of respondents reported that they cast votes in the most recent elections
but only 60% of the eligible voters actually voted.

Respondents is your clue. Did all who were eligible responded or only the ones who voted responded

Points directly to C.

Please let me me know if this is the right explanation

yes, that's the idea!

_________________
Tim Sanders
Manhattan GMAT Instructor

hi tim,

although the group of respondents and the group of persons who actually voted may be different,i do not get how option c helps to explain the discrepancy between the two statistics.For instance, suppose we fix the number of "eligibles" to vote at 100.Hence the number of eligibles who "actually voted" is 60(60%).still there are 3 possibilities with respect to number of persons who responded to the survey,
1)no.of respondents(e.g.200)>no. of eligibles(100)
so,71% of 200 =142 and discrepancy is 82(142-60)
2)no.of respondents(e.g.100)=no. of eligibles(100)
so,71% of 100 =71 and discrepancy is 11(71-60)
3)no.of respondents(e.g.50)<no. of eligibles(100)
so,71% of 50 =35 and discrepancy is -25(35-60)
ony one case when total no.of respondents is 84 ,it does not give any discrepancy.(60-60=0)and this case can not be explained by the option c.i.e" 60 persons are more likely to respond than the other 40 persons" does not help.Where as if option E is accepted ,it can resolve that discrepancy of 24(84-60).

need ur help

satyaking,
Let's review what we know:
71% of respondents to a poll said that they voted.
60% of all eligible voters actually voted.

Which one explains this best?

The poll respondents are a small subset of all eligible voters. What if we know that this particular subgroup happen to vote more often than the overall pool of eligible voters? That would explain why 71% of poll respondents say that they voted, but only 60% of eligible voters voted. Does this help?

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Jamie Nelson
ManhattanGMAT Instructor