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Hit and Run case ! The argument hits on one group and then starts talking about another group. The catch is 70% of merchandise orders can be placed by any of the 2 groups - over 35 yrs and exactly 35 yrs

30% of merchandise orders come from source X (subscribers) 70% of merchandise orders will come from different source. And composition of this group is unknown.

A cannot be necessarily true. B cannot be inferred. C makes a wrong assumption that over 35 yr group has placed more merchandise orders. What if the 35 yr group has placed most orders? D is out of scope since we don't know the order value in different groups E Answer _________________

Yes, this is definitely E. The two surveys discuss different groups of people. The first is a survey of *subscribers* to the magazine. The second discusses *all* people who bought merchandise in response to magazine ads. Both claims can be true if a lot of under-35 non-subscribers bought merchandise, which is what E says. _________________

Nov 2011: After years of development, I am now making my advanced Quant books and high-level problem sets available for sale. Contact me at ianstewartgmat at gmail.com for details.

I said (C). I don't understand how it can be (E) - you don't really have the information to determine how many non-subscribers placed orders, which is what (E) is talking about. For example, what if 100 subscribers placed orders, and 30 of them were under age 35, while only 5 non-subscribers placed orders, and 4 of them were under age 35? Then both findings are still correct, but (E) is false (unless we're going on some very arbitrary definition of "many").

No, you may have misinterpreted one of the two findings. The second finding says that most orders were placed by people under 35; that includes orders from both subscribers and non-subscribers. I think you are interpreting that finding to be about orders from non-subscribers only, but it's not. So in your hypothetical example, you have 105 orders in total, but still, only 34 orders come from people under the age of thirty-five. That isn't consistent with the second finding in the stem which tells us that most orders come from under-thirty-fives, so is not a possible scenario.

TehJay wrote:

(C) fits both findings the best. 70% of subscribers who placed orders were age 35 or over, a big majority. The only way to make (C) not true is if the number of non-subscribers who placed orders is larger than the number of subscribers who placed orders - and even then, you can't really determine whether or not the 30% of subscribers under 35 + the "most" of non-subscribers under 35 outnumber the 70% of subscribers + the remaining non-subscribers.

It's actually mathematically impossible for C to be true. Say you have S subscribers and N non-subscribers who placed orders. We know that 0.7S orders came from subscribers over thirty-five. Say you have X orders in total from non-subscribers over 35. We know from the second finding that less than half of all orders come from people over thirty-five, so:

(0.7S + X)/(N+S) < 1/2

But the proportion of all orders coming from subscribers over thirty-five is 0.7S/(N+S), and this is clearly less than the left side of the inequality above, so must be less than one half. So it's impossible for 'most' orders to have come from subscribers over thirty-five, and C cannot be true. _________________

Nov 2011: After years of development, I am now making my advanced Quant books and high-level problem sets available for sale. Contact me at ianstewartgmat at gmail.com for details.

I said (C). I don't understand how it can be (E) - you don't really have the information to determine how many non-subscribers placed orders, which is what (E) is talking about. For example, what if 100 subscribers placed orders, and 30 of them were under age 35, while only 5 non-subscribers placed orders, and 4 of them were under age 35? Then both findings are still correct, but (E) is false (unless we're going on some very arbitrary definition of "many").

(C) fits both findings the best. 70% of subscribers who placed orders were age 35 or over, a big majority. The only way to make (C) not true is if the number of non-subscribers who placed orders is larger than the number of subscribers who placed orders - and even then, you can't really determine whether or not the 30% of subscribers under 35 + the "most" of non-subscribers under 35 outnumber the 70% of subscribers + the remaining non-subscribers.

Really it seems like the question doesn't give you enough info to properly answer it, but I think (C) is a better answer than (E), given the assumptions you have to make to choose either one.

i think E correct because E can be translated to the assumption that many people under the age of 35 who read the advertisement on the magazine decided to order merchandise but many of them did not buy magazine. They could read by chance. C is counter fact. _________________

Consider giving me kudos if you find my explanations helpful so i can learn how to express ideas to people more understandable.

Yes, this is definitely E. The two surveys discuss different groups of people. The first is a survey of *subscribers* to the magazine. The second discusses *all* people who bought merchandise in response to magazine ads. Both claims can be true if a lot of under-35 non-subscribers bought merchandise, which is what E says.

Hi Ian,

i am still confused..can you elaborate a bit more please.

Findings of magazine: 30% of the orders placed by subscribers in response to advertisements were placed by subscribers under the age 35.

Findings of the advertiser: most of the orders placed in response to advertisements were placed by people under the age 35.

As already illustrated by nusmavrik the argument subtly shifts from subscribers to general population.

Most in advertiser's finding means >50%.

Let us assume total 100 orders were placed in response to advertisement in the magazine. Therefore at least 50 people who ordered were under the age of 35 as per advertiser's finding.

In case all the above 100 people were subscribers of the magazine. Which means only 30 people under the age of 35 placed the order.

It follows from above that orders placed by subcribers = total orders placed cannot be true, since advertiser's survey finding states that 50 people were under 35. Moreover number of orders placed by subscribers cannot be more than total orders placed.

Therefore the orders placed by subscribers has to be less than the total number of orders, ==>ie. part of the orders were placed by non subscribers of the magazine. _________________

Sun Tzu-Victorious warriors win first and then go to war, while defeated warriors go to war first and then seek to win.

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