Let's try this:

Valerie's argument sounds pretty fishy, huh? In fact, it would be amazing if 80% of the world's population knew someone from the US. After all, the overwhelming majority of American live in one place--America! Valerie's logic would only apply if Americans were distributed more or less evenly among the globe, which they clearly are not. Many people in China, India, Africa, and South America would never have had the opportunity to meet anyone from the US.

The same assumption exists in Deb and Erik's discussion; the reason it's harder to spot is because in the case of graduation rates, the its not obvious incorrect. One could perfectly reasonably assume that students drop out at relatively consistent rates across a small country. But what if they didn't? If ALL the country's dropouts were normally confined to one or two provinces, but now 80% of the entire country's population knows a dropout, Erik would be mistaken. Deb's statistic would be cause for alarm, as it would indicate the problem was spreading! On the other hand, if the 10% dropout rate was universal across the country, then Erik is right: Deb's statistic is unsurprising and not alarming. Thus, (B) clearly identifies the assumption in Erik's argument.

Hope this helps!

Deb: It ’ s worrisome that 80% of the people in this country know at least one person who did not finish high school.

Erik: But the average person has about one hundred different acquaintances, so, even if the normal high school dropout rate is only 10%, most people will probably know at least one dropout.

Erik ’ s argument relies on the assumption that:

A The normal dropout rate has remained very stable over time.
Irrelevant

C The number of people who know a dropout is usually over 80% of the population.
This doesn't help.

D The statistics cited by Deb don’t overstate the fraction of the population that actually does know a high school dropout.
This seems to be a validation of Debs statement. Doesn't help.

E Being personally acquainted with a dropout causes more anxiety about the dropout problem than do the dropout statistics themselves.
Irrelevant

B The dropout rate varies little from region to region across the country.
Correct answer. The drop out rate has to be uniform across the country for Erik's argument to hold good. If there is an area where the drop out rate is much lower than 10% then the probability of everyone knowing at least 1 dropout (out of a 100 acquaintances) falls.

Eric says "most people will probably know at least one dropout."

in option B "B The dropout rate varies little from region to region across the country.
Correct answer. The drop out rate has to be uniform across the country for Erik's argument to hold good. If there is an area where the drop out rate is much lower than 10% then the probability of *everyone *knowing at least 1 dropout (out of a 100 acquaintances) falls."

Eric never stated that *Everyone* knew atleast 1 dropout, but "most of the people".
So the answer should be "C"

Experts, please comment...

if you negate C- it does not weaken the argument, thus it is not an assumption. But if you negate B, the conclusion of Eric will be weaken as the statistical data used will be questioned.
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It will be B as its clear that Erik has assumed the drop rate is same all across the country. If you negate this point, his argument weakens..

Stumped on this one. No clue. Will wait for the enlighted souls to share their perspective on this one.

Can some one explain how can some body arrive at the conclusion "most people will probably know at least one dropout" based on premise "the average person has about one hundred different acquaintances, and the normal high school dropout rate is only 10%" .

For assumption questions. Negate the answer choice, and if that neagted answer choice weakens the arguement , thats the assumption.
So, if an average person know about one hundred different acquaintances located in only one specific area, not every part of the country then the argument is weaken.
Here, negate choice B - "The dropout rate varies little from region to region across the country. Which will be changed as" – “The dropout rate varies little from region to region across the country”.

The gist of the argument presented by eric is eryone has 100 acquaintances , so there are more chances of people knowing drop-outs in common.
The conclusion is not the probability that everyone knows at least 1 drop - out. The conclusion is that "That more than 80 % of people know a dropout is not worrisome"
What he says is "so what if 80% people know a dropout,even if the drop out rate is miniscule ,80% of the populate will know dropouts in common because 1 has 100s of friends. and they could have a dropout friend in common as common friend just the way it is on facebook.
So if we negate option B, we get "the normal dropout rate varies a lot from place to place "and in this case it does become a cause of concern , if the dropout rate in Oklahoma is 10% and the dropout rate in california is 60%.
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hi eli, thanks for the intervention.What i cudnt get from your explanation is "the statistic is a case for alarm in case the % of drop outs may vary from region to region or the dropout percentage may increase in a few places?
My explanation takes the variation in percentage into consideration but not variation from region to region.
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Hi mundasingh,

I'm not quite sure what you're asking; can you clarify?

Thanks!

Hi Eli,
You had written
One could perfectly reasonably assume that students drop out at relatively consistent rates across a small country. But what if they didn't? If ALL the country's dropouts were normally confined to one or two provinces, ----- Deb's statistic would be cause for alarm, as it would indicate the problem was spreading!
so does this mean that even if the rate was consistently 10% but spread uniformly all over the country, would it be cause for alarm ?
I had only taken consistent rates into consideration in the explanation that i had offered just before you posted.My take was : If the rate was 10 % in 1 province and 60% in other provinces, it would be cause for alarm.
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Hi mundasingh,

Erik's point was that even a very low dropout rate (10%) could account for Deb's statistic, and therefore Deb's statistic is not cause for alarm.

However, Erik's example would only work if the 10% dropout rate he offered as an example were spread evenly across the country. If low graduation rates are normally confined to a specific area, then Erik would be wrong; Deb's statistic that 80% of the population knows someone who left high school would be quite worrying, because it would indicate that the problem is beginning to spread to other parts of the country.

Thanks for confirming this Eli.I got your point and the line of reasoning. This hardly involve dany maths as 1 guy was professing
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thanks a lot.... thanks for your information... very much useful for me....

amitysoft dot com

Eli,

A quick question here, as you mentioned earlier, the impt point here is that the assumption will make Deb's statistic unsurprising and not alarming. In that case, wouldn't answer C also be a good candidate for the correct answer.

Kindly get back when possible, thanks.

The questions asks about an assumption made by Erik's argument. (C) might tangentially strengthen Erik's conclusion, but it has nothing to to with his reasoning.

To be honest I can't seem to be able to grasp any of the reasoning given in the posts above.

For my understanding, lets divide the country in 2 regions. West and East, with a population of 500 each.

Deb finds it alarming that 80% of people know a dropout i.e. (800 people out of 1000 know a dropout in the country).
Erik says nothing to worry about because the dropouts are really low, its just that the same dropout may be an acquaintance of more than 1 person, since an avg person has around 100 acquaintances.

Negating B:
Drop our rate varies a LOT from region to region
Now lets say in East the dropout rate is 10% (i.e. 50 drop outs amongst a population of 500), and in West its 20% (i.e. 100 drop outs out of a total of 500)
So in total we have 150 drop outs from 1000.

How does this in any way prove or disprove that amongst these 800 people no SINGLE person will or will not know more than 1 drop out? If A knows B who is a drop out from those 150, why is it unlikely that A can't know 99 other non-drop outs?

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