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# Many gardeners believe that the variety of clematis vine that is most

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Re: Many gardeners believe that the variety of clematis vine that is most [#permalink]
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The best way to answer this question is via negation technique.

A states - "The nursery sells more than 10 different varieties of clematis"
Negate A: The nursery sells less than 10 different varieties of clematis. --> Out of 1 million if less than 10 varieties are sold, then there is atleast one variety ( >10% popularity) which is more popular than Jackmanii (10% popularity) --> Conclusion breaks down.

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Re: Many gardeners believe that the variety of clematis vine that is most [#permalink]
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Many of the explanations here are completely correct, so I'm not sure that I have anything astoundingly new to add to the discussion. But we've had a few requests for expert help, so I'll give this a whirl.

For Arpit, among others: I think that part of the confusion is that we're looking for an assumption that's necessary. That doesn't always mean that it's going to be 100% airtight, or that you'll be able to reach the conclusion with 100% certainty based on that assumption. But the correct answer will be something that's needed to draw the conclusion, even if it's not enough by itself.

In other words: without that assumption, the conclusion couldn't hold.

I see lingering doubts in the thread about why (E) is wrong and why (A) is right.

Quote:
(E.) For all nurseries in North America that specialize in clematis, at least 10% of the clematis plants they sell are jackmanii.

This is admittedly a little bit tempting: sure, it would strengthen the argument. But this isn't a strengthen question: we need to know whether this is NECESSARY to draw the conclusion that "the variety of clematis vine that is most popular among gardeners in North America."

And it isn't necessary: even if (E) is NOT true -- for example, if jackmanii accounts for less than 10% of clematis plants at a few nurseries -- it's still possible that jackmanii is the most popular. And since (E) isn't necessary, it's not the correct answer.

Quote:
(A) The nursery sells more than 10 different varieties of clematis

This NEEDS to be true. If the nursery sells fewer than 10 different varieties, then there's no way that jackmanii -- with a market share of 10% at the biggest nursery -- could possibly be #1. This is absolutely necessary to draw the conclusion -- and therefore our correct answer.

But again, (A) isn't necessarily sufficient by itself, either: you could have 20 varieties, and jackmanii could, in theory, be beaten out by one or more of them. But you still need to assume that there are more than 10 in order for jackmanii to be #1. The key takeaway: an assumption can be 100% necessary (and therefore the correct answer), while still leaving possibilities for the conclusion to be false.
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Re: Many gardeners believe that the variety of clematis vine that is most [#permalink]
sayantanc2k and other experts
Conclusion is belief is correct , now what is that belief; the variety of clematis vine that is most popular among gardeners in North America is jackmanii.
Here I thought we are talking about whole NA gardeners

premise to help on this will be based on single nursery, which is largest one. from here I started making assumptions .......
1) There must be other nurseries , which sell "varieties of clematis" and if they sell jackmanii as there also with highest percentage , then we can conclude the jackmanii is most popular one. I straight way discard A because it is talking about one nursery.

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Re: Many gardeners believe that the variety of clematis vine that is most [#permalink]
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mbaprep2016 wrote:
sayantanc2k and other experts
Conclusion is belief is correct , now what is that belief; the variety of clematis vine that is most popular among gardeners in North America is jackmanii.
Here I thought we are talking about whole NA gardeners

premise to help on this will be based on single nursery, which is largest one. from here I started making assumptions .......
1) There must be other nurseries , which sell "varieties of clematis" and if they sell jackmanii as there also with highest percentage , then we can conclude the jackmanii is most popular one. I straight way discard A because it is talking about one nursery.

The main point of the argument is as follows:

The belief is based on the fact that among all varieties of clematis, the jackmanii is the variety that is sold the most by the largest nursery.

Now if jackmanii constitutes 10% of the total sales by the nursery, then there must be more than ten varieties sold by the nursery - if there had been 10 or less no. of varieties sold, then there would have been at least one other variety that was sold 10% or more and thus jackmanii would not have been the one that was sold the most by the largest nursery.
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Re: Many gardeners believe that the variety of clematis vine that is most [#permalink]
Hi,
The question says jackmanii is the most popular among gardeners. It doesn't say that the best selling plant of this largest nursery is jackmanii . Jackmani might be the most popular plant in the whole country but this particular nursery might be selling another flower more. So how do we know that sales share of Jackmani ,%10, is the largest in this nursery?What am I missing?
Thanks.
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Re: Many gardeners believe that the variety of clematis vine that is most [#permalink]
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deucebigalow wrote:
Hi,
The question says jackmanii is the most popular among gardeners. It doesn't say that the best selling plant of this largest nursery is jackmanii . Jackmani might be the most popular plant in the whole country but this particular nursery might be selling another flower more. So how do we know that sales share of Jackmani ,%10, is the largest in this nursery?What am I missing?
Thanks.

The conclusion is that the belief--that jackmanii is the most popular variety of clematis vine among North American gardeners--is apparently correct. In other words, the evidence in the passage should support the belief of those gardeners. This does not mean that the evidence in the passage has to prove that the belief is accurate.

The conclusion is that the belief is apparently correct, not that the belief must be true. So, even if we could come up with scenarios that would make that belief inaccurate, the reasoning and conclusion in this passage would not be impacted.

This sets us up for choice (A), as described below: https://gmatclub.com/forum/many-gardene ... l#p1834817
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Re: Many gardeners believe that the variety of clematis vine that is most [#permalink]
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In option A- The nursery sells more than 10 different varieties of clematis. Suppose, the nursey sells 12 varieties. Of the 12 varieties, suppose 10 varieties are sold at 5 % each, jackmanii at 10% and the other one at 40%. So, howcan we say that Jckamnii si the most popular considering that the sales of someone else is greater than 10%.Also, nowhere in the premise it's given that 10% is the highest sale.
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Re: Many gardeners believe that the variety of clematis vine that is most [#permalink]
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sunny91 wrote:
In option A- The nursery sells more than 10 different varieties of clematis. Suppose, the nursey sells 12 varieties. Of the 12 varieties, suppose 10 varieties are sold at 5 % each, jackmanii at 10% and the other one at 40%. So, howcan we say that Jckamnii si the most popular considering that the sales of someone else is greater than 10%.Also, nowhere in the premise it's given that 10% is the highest sale.

As explained in the explanation above, we do not need to PROVE that jackmanii is the most popular variety in NA or even that it is the most popular variety at the nursery. But if jackmanii is NOT the most popular variety at the nursery, then the author's argument falls apart.

If the nursery sells fewer than ten varieties, then there is no way that jackmanii is more popular than all of the others. At best, if there are exactly ten varieties, then jackmanii might be tied for #1. And if there are fewer than 10 varieties, then there MUST be other type that accounts for more than 10% of sales.

It is absolutely true that even with more than 10 varieties, jackmanii might not be #1. But in order for jackmanii to be #1, you MUST assume that there are more than 10 varieties. Choice (A) does not prove that the conclusion is true, but the conclusion CANNOT be true unless (A) is assumed. That makes (A) a required assumption.
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Re: Many gardeners believe that the variety of clematis vine that is most [#permalink]
GMATNinja wrote:
But what about the other 90%? What if another variety of clematis accounts for MORE than 10% of the one million? In that case, jackmanii would not be the most popular variety at the nursery. However, if no other variety accounts for 10% (or more) of the one million, then jackmanii would be in fact be the most popular variety at the nursery.

Would that prove that jackmanii is the most popular variety in NA? Not necessarily. But if jackmanii is #1 at the largest nursery, that's certainly EVIDENCE that jackmanii is #1 in NA. Again, we are trying to conclude that the belief is APPARENTLY correct, not that the believe is DEFINITELY correct. As long as we have evidence that jackmanii is the most popular variety among NA gardeners, we're in good shape.

Quote:
(A) The nursery sells more than 10 different varieties of clematis
If the nursery sells 10 varieties or fewer, then there would HAVE to be another variety that accounts for more than 10% of the one million plants sold at the nursery. If that were true, then jackmanii could not be the most popular variety at the nursery. Thus, we would not have evidence that jackmanii is #1 in NA. Without choice (A), the argument falls apart.

Now, does choice (A) PROVE that jackmanii is #1 at the nursery? Not at all... even with 20 varieties, there could be another type that accounts for more than 10% of the million. That, of course, would ruin the argument.

Even if choice (A) is true, the argument may or may not be valid, but that's okay. In other words, choice (A) doesn't PROVE that the author's reasoning is sound. But without choice (A), the author's argument could not be valid. This is a required assumption, so keep (A).

Dear GMATNinja or GMATNinjaTwo,

#1 a big gap btw the premises and conclusion
GMATNinja wrote:
premises:
The largest clematis nursery in NA sells one million clematis plants per year.
Of the one million clematis plants sold per year by that nursery, ten percent are jackmanii.

conclusion: he gardener's belief--that jackmanii is the most popular variety of clematis vine among gardeners in North America (NA)--is apparently correct

Anyone think that this argument has a gap that generalizes (NA)from a special nursery (the largest nursery)
even as the premises above, it does not lead to the conclusion, a top sale in the largest nursery does not mean the most popular in NA (North America),
it is highly possible that the others nurseries expect the largest one sells one kind of clematis vines, say X, far more then the largest one sales jackmanii, the top sales.
Then X is much more popular than jackmanii,
see, we can weaken the most popular,
So it seems not so closely that lead to conclusion

One reason i haven't gotten A is correct.

#2what's assumption?
Seems i haven't gotten what assumption.

IMO, assumption is one unstated premise, which the author believes conclusion MUST BE TRUE if based the assumption.

That why i did not understand a part of your explanation :
Even if choice (A) is true, the argument may or may not be valid, but that's okay. In other words, choice (A) doesn't PROVE that the author's reasoning is sound.

if the argument is invalid, does it still be an assumption, seems it does NOT consist with the definition of assumption.

another reason i did not get A is correct.

#3 what's required assumption
Is required assumption a segment of assumption. if is, then required assumption has the character, the conclusion MUST BE TRUE based on required assumption, right?

#4 difference bwt "apparently" and "definitely"
As you mentioned, The conclusion would be substantially different if we were to replace "apparently" with "definitely".
you emphase "PROVE" , a word leading me to consider it a strengthen question, I think i must miss something, would you please help?

Have a nice day
>_~

Originally posted by zoezhuyan on 26 Mar 2018, 00:30.
Last edited by zoezhuyan on 26 Mar 2018, 05:17, edited 3 times in total.
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Re: Many gardeners believe that the variety of clematis vine that is most [#permalink]
zoezhuyan wrote:
GMATNinja wrote:
But what about the other 90%? What if another variety of clematis accounts for MORE than 10% of the one million? In that case, jackmanii would not be the most popular variety at the nursery. However, if no other variety accounts for 10% (or more) of the one million, then jackmanii would be in fact be the most popular variety at the nursery.

Would that prove that jackmanii is the most popular variety in NA? Not necessarily. But if jackmanii is #1 at the largest nursery, that's certainly EVIDENCE that jackmanii is #1 in NA. Again, we are trying to conclude that the belief is APPARENTLY correct, not that the believe is DEFINITELY correct. As long as we have evidence that jackmanii is the most popular variety among NA gardeners, we're in good shape.

Quote:
(A) The nursery sells more than 10 different varieties of clematis
If the nursery sells 10 varieties or fewer, then there would HAVE to be another variety that accounts for more than 10% of the one million plants sold at the nursery. If that were true, then jackmanii could not be the most popular variety at the nursery. Thus, we would not have evidence that jackmanii is #1 in NA. Without choice (A), the argument falls apart.

Now, does choice (A) PROVE that jackmanii is #1 at the nursery? Not at all... even with 20 varieties, there could be another type that accounts for more than 10% of the million. That, of course, would ruin the argument.

Even if choice (A) is true, the argument may or may not be valid, but that's okay. In other words, choice (A) doesn't PROVE that the author's reasoning is sound. But without choice (A), the author's argument could not be valid. This is a required assumption, so keep (A).

Dear GMATNinja or GMATNinjaTwo,

#1 a big gap btw the premises and conclusion
GMATNinja wrote:
premises:
The largest clematis nursery in NA sells one million clematis plants per year.
Of the one million clematis plants sold per year by that nursery, ten percent are jackmanii.

conclusion: he gardener's belief--that jackmanii is the most popular variety of clematis vine among gardeners in North America (NA)--is apparently correct

Anyone think that this argument has a gap that generalizes (NA)from a special nursery (the largest nursery)
even as the premises above, it does not lead to the conclusion, a top sale in the largest nursery does not mean the most popular in NA (North America),
it is highly possible that the others nurseries expect the largest one sells one kind of clematis vines, say X, far more then the largest one sales jackmanii, the top sales.
Then X is much more popular than jackmanii,
see, we can weaken the most popular,
So it seems not so closely that lead to conclusion

One reason i haven't gotten A is correct.

#2what's assumption?
Seems i haven't gotten what assumption.

IMO, assumption is one unstated premise, which the author believes conclusion MUST BE TRUE if based the assumption.

That why i did not understand a part of your explanation :
Even if choice (A) is true, the argument may or may not be valid, but that's okay. In other words, choice (A) doesn't PROVE that the author's reasoning is sound.

if the argument is invalid, does it still be an assumption, seems it does NOT consist with the definition of assumption.

another reason i did not get A is correct.

#3 what's required assumption
Is required assumption a segment of assumption. if is, then required assumption has the character, the conclusion MUST BE TRUE based on required assumption, right?

#4 difference bwt "apparently" and "definitely"
As you mentioned, The conclusion would be substantially different if we were to replace "apparently" with "definitely".
you emphase "PROVE" , a word leading me to consider it a strengthen question, I think i must miss something, would you please help?

Have a nice day
>_~

The author is simply arguing that there is evidence suggesting that jackmanii is #1 in NA. Yes, it is possible that, despite this evidence, jackmanii is not #1. We don't care about that possibility. As long as jackmanii is #1 at the nursery, then we have evidence that it is #1 in NA. In other words, in that case, jackmanii is apparently #1 in NA. This absolutely does not prove that jackmanii is #1, but the author is not trying to prove anything.

Consider the following example:

• Most Americans believe that the Big Mac is the most popular sandwich at McDonalds.
• This belief is apparently correct. A recent study looked at sales of the 1,000 highest-revenue-generating McDonalds in the US. The number of Big Macs sold at those restaurants was twice as large as the number of any other sandwich sold.

Does that PROVE that Big Macs are #1 in the US? Nope. But the argument is not concerned with proving anything. The argument simply says that the evidence supports the belief of most Americans. So even if Big Macs are NOT #1, the logic of this argument is not flawed. Similarly, the argument in the passage is not invalid at all, regardless of whether clematis is actually #1.

I hope that helps!
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Re: Many gardeners believe that the variety of clematis vine that is most [#permalink]
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GMATNinja wrote:
The conclusion of this passage is that the gardener's belief--that jackmanii is the most popular variety of clematis vine among gardeners in North America (NA)--is apparently correct. The word "apparently" is very important here. The conclusion would be substantially different if we were to replace "apparently" with "definitely".

More on that in a moment... but first, why does the author conclude that the belief is apparently correct?

• The largest clematis nursery in NA sells one million clematis plants per year.
• Of the one million clematis plants sold per year by that nursery, ten percent are jackmanii.

A substantial chunk of the clematis plants sold at the largest nursery are jackmanii. The author reasons that jackmanii's popularity at the largest nursery is a good indicator of its popularity among NA gardeners.

But what about the other 90%? What if another variety of clematis accounts for MORE than 10% of the one million? In that case, jackmanii would not be the most popular variety at the nursery. However, if no other variety accounts for 10% (or more) of the one million, then jackmanii would be in fact be the most popular variety at the nursery.

Would that prove that jackmanii is the most popular variety in NA? Not necessarily. But if jackmanii is #1 at the largest nursery, that's certainly EVIDENCE that jackmanii is #1 in NA. Again, we are trying to conclude that the belief is APPARENTLY correct, not that the believe is DEFINITELY correct. As long as we have evidence that jackmanii is the most popular variety among NA gardeners, we're in good shape.

With that in mind, let's look at the answer choices:

Quote:
(A) The nursery sells more than 10 different varieties of clematis

If the nursery sells 10 varieties or fewer, then there would HAVE to be another variety that accounts for more than 10% of the one million plants sold at the nursery. If that were true, then jackmanii could not be the most popular variety at the nursery. Thus, we would not have evidence that jackmanii is #1 in NA. Without choice (A), the argument falls apart.

Now, does choice (A) PROVE that jackmanii is #1 at the nursery? Not at all... even with 20 varieties, there could be another type that accounts for more than 10% of the million. That, of course, would ruin the argument.

Even if choice (A) is true, the argument may or may not be valid, but that's okay. In other words, choice (A) doesn't PROVE that the author's reasoning is sound. But without choice (A), the author's argument could not be valid. This is a required assumption, so keep (A).

Quote:
(B) The largest clematis nursery in North America sells nothing but clematis plants

The nursery could sell many other types of plants. As long as jackmanii is the most popularity variety of clematis plant sold at the nursery, then the author's reasoning holds up. This is not a required assumption, so eliminate (B).

Quote:
(C) Some of the jackmanii sold by the nursery are sold to gardeners outside North America

If a substantial portion of jackmanii sales were to gardeners outside of NA, then we might have a problem. That might suggest that jackmanii's popularity at the nursery is NOT a good indicator of jackmanii's popularity among NA gardeners.

Choice (C) only says that SOME of the jackmanii are sold to gardeners outside of NA. In that case, the jackmanii sales at the nursery are probably a good indicator of its popularity among NA gardeners.

Does that make (C) a REQUIRED assumption? If (C) were not true and the nursery ONLY sold jackmanii to gardeners within NA, then that would probably further strengthen the argument. That would give us even more reason to believe that the sales at the nursery are a good indicator of NA popularity. Choice (C) is not a required assumption, so eliminate (C).

Quote:
(D) Most North American gardeners grow clematis in their gardens

It doesn't matter whether clematis is a popular plant in general. The belief is that jackmanii is the most popular variety OF clematis. Even if only a tiny fraction of NA gardeners grow clematis, jackmanii could still be the most popular variety among those gardeners who DO grow clematis. Eliminate (D).

Quote:
(E) For all nurseries in North America that specialize in clematis, at least 10% of the clematis plants they sell are jackmanii.

This is admittedly a little bit tempting: sure, it would strengthen the argument. But this isn't a strengthen question: we need to know whether this is NECESSARY to draw the conclusion.

And it isn't necessary: even if (E) is NOT true -- for example, if jackmanii accounts for less than 10% of clematis plants at a few nurseries -- it's still possible that jackmanii is the most popular. And since (E) isn't necessary, it's not the correct answer.

Even if A is not true the conclusion can be true. Consider a situation in which there are only two variety of clematis & the largest nursery export the other variety (which consists of 90%) to neighboring country and all of jackmanii's (10%) to NA still jackmanii's will be most popular, hence option A is not necessary for the conclusion to be true.
Please explain where I am making mistake?
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All credits to CR Bible: This is an excerpt of my personal review session. Hope it helps:

First of all – before starting keep in mind that there are two types of assumptions: i) supporter assumptions and ii) defender assumptions. Let’ s provide an example of both:

i) Support assumption are assumptions that link together new elements in the stimulus or fill logical gaps in the argument. An example of this would be:

All male citizens of the Netherlands have the right to smoke weed. Therefore, Riccardo has the right to smoke weed in the Netherlands. The supporter assumption here is that Riccardo is a male citizen.

The fact that we assume Riccardo is a male citizen contains a piece of information not previously mentioned in the stimulus. In this case, Riccardo is a new element in the conclusion. This creates a gap in the conclusion. Therefore – the supporter assumption plays a paramount role in bringing these two terms together. Another example of this supporter assumption is:

All ducks in Martinique that have a really big beak are treated as holy and can therefore not be eaten by the local residents of Martinique. Therefore, Duckie, my favorite duck that I visit every day can’t be eaten by the local residents of Martinique.

The new element in the argument here is Duckie! The supporter assumption links this new piece of information together with the previous element. By assuming that Duckie has a really big beak.

ii) Defender assumptions are assumptions that contain statements that eliminate ideas or assertions that would undermine the conclusion. In some way, they defend the argument by showing that a possible source of attack is eliminated. Let’s take an example of this:

People who exercise a lot more perform better academically. Thus, exercising must cause a person to improve his/her grades. The author assumes here that the following assumptions aren’t true:

i) Sleeping more than eight hours a day doesn’t improve one’s grades.
ii) A high protein diet doesn’t enable someone to study more effectively and therefore improve their grades.

These hidden assumptions protect the argument against statements that would undermine the conclusion. Simply put, the author assumes that every alternate cause doesn’t exist!

Now let’s pivot back to the exercise at hand:

Many gardeners believe that the variety of clematis vine that is most popular among gardeners in North America is jackmanii. This belief is apparently correct since, of the one million clematis plants sold per year by the largest clematis nursery in North America, ten percent are jackmanii.
Which of the following is an assumption on which the argument depends?

(A) The nursery sells more than 10 different varieties of clematis
(B) The largest clematis nursery in North America sells nothing but clematis plants
(C) Some of the jackmanii sold by the nursery are sold to gardeners outside North America
(D) Most North American gardeners grow clematis in their gardens
(E) For all nurseries in North America that specialize in clematis, at least 10% of the clematis plants they sell are jackmanii.

Reviewing the stimulus we see:

Conclusion: The most popular variety clematis vine amongst gardeners in North America is jackmanii.

Premise: Of the one million clematis plants sold per year, by the largest clematis nursey in North America, ten percent are jackmanii.

Prephrase:
The new element in this stimulus here is the largest clematis nursery in North America. Remember that a supporter assumption brings together two pieces of new information. This would imply that the pieces sold at the largest clematis nursey are representative of the rest of the country. So we need a supporter assumption!

Let’s review the answer choices with this prephrase in mind:

a) The nursery sells more than 10 different varities of clematis. This would mean that the nursery indeed, is representative of the entire clematis vine population. If they would just sell two species, this would imply that that the jackmani is the least popular. This answer choise directly links the premise with the conclusion of the argument. CONTENDER!

b) Ok – if it only sells clematis plants that’s great for them. But does it really tell us anything about the variety of clematis vine? This answer choice is tricky, as it requires us to specifically understand what is being said. The word variety is key.

c) Some… This would merely imply that it is popular outside North America – but the conclusion focusses on inside North America. Out of scope.

d) Great for them – what is most? This would strengthen it in some way. But is it the underlying assumption that holds the premise and conclusion together? No. Because if most NA gardeners grow it in this garden, this doesn’t tie together the element regarding the largest clematis nursery and the conclusion. Remember that this is an assumption question and not a strengthener.

e) This was my first answer choice – as it slightly matched my prephrase, but it’s wrong because: we still don’t know the amount of varieties each nursery holds. And therefore, doesn’t logically link the premise with the conclusion. Because it could still mean that the other nurseries sell only two/three varieties. Let’s label it as a contender for now.

Deciding between the two contenders A and E

Let’s use the assumption negation technique to decide between the two contenders. The assumption negation technique simply determines whether the negated answer choices weaken the argument, and therefore help identify the lynchpin of the argument - the assumption that holds the premise and conclusion together: the central nervous system, heart or brain whatever metaphor we want to use.

The assumption negation technique consists of two steps:

i) Logically negate the answer choices under consideration.
ii) The negated answer choice that attacks the argument will be the correct answer.
Understand that the consequence of negating an assumption is that the validity of the conclusion is called into question. So when we take away (negate it) the assumption – the building block of the argument – the entire reasoning structure is called into question.

Let’s negate:
a) The nursery doesn’t sell more than 10 different varieties of clematis.

b) For all nurseries in North America that specialize in clematis, at least 10% of the clematis plants they don’t sell are jackmanii. So 90% sold aren’t jackmani.

Which one of these weakens the argument?

If the nursery doesn’t sell more than 10 different varieties of clematies, this would mean that the 10% sold is actually less than the majority. If it sells 10 varieties for example, it is a mere 10% of the other varities, which would directly attack the premise and make weaken the argument the most. Therefore answer A is the right choice between A and E. For E – this would still mean that 10% sold are Jackmani and therefore doesn’t weaken the argument at all and is therefore not a supporter assumption that links the two pieces of information together.

So answer choice is A: for the simple fact that it’s a support assumption and when negated, the argument doesn’t hold, and we can therefore conclude that A is the entire lynchpin of the argument holding the premise and conclusion together.

Originally posted by CLIMBTHELADDER on 17 Apr 2018, 03:54.
Last edited by CLIMBTHELADDER on 28 Dec 2018, 13:32, edited 1 time in total.
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Re: Many gardeners believe that the variety of clematis vine that is most [#permalink]
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Even if A is not true the conclusion can be true. Consider a situation in which there are only two variety of clematis & the largest nursery export the other variety (which consists of 90%) to neighboring country and all of jackmanii's (10%) to NA still jackmanii's will be most popular, hence option A is not necessary for the conclusion to be true.
Please explain where I am making mistake?

aditya201819, try reviewing these two posts:

Yes, even if there are fewer than ten varieties, jackmanii COULD still be the most popular in NA. And even if there are MORE than ten varieties, it might not be. But that's not the point. The question does NOT ask, "Which of the following must be true for jackmanii to be the most popular in NA?". The question asks, "Which of the following is an assumption on which THE AUTHOR'S LOGIC depends."

The author's conclusion is NOT: "Jackmanii is DEFINITELY the most popular in NA." The author's conclusion is that the belief is apparently correct. In other words, the author believes that the sales data from the nursery is EVIDENCE suggesting that the belief is true. Whether jackmanii is ACTUALLY the most popular is irrelevant.
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Re: Many gardeners believe that the variety of clematis vine that is most [#permalink]
GMATNinja wrote:
The conclusion of this passage is that the gardener's belief--that jackmanii is the most popular variety of clematis vine among gardeners in North America (NA)--is apparently correct. The word "apparently" is very important here. The conclusion would be substantially different if we were to replace "apparently" with "definitely".

More on that in a moment... but first, why does the author conclude that the belief is apparently correct?

• The largest clematis nursery in NA sells one million clematis plants per year.
• Of the one million clematis plants sold per year by that nursery, ten percent are jackmanii.

A substantial chunk of the clematis plants sold at the largest nursery are jackmanii. The author reasons that jackmanii's popularity at the largest nursery is a good indicator of its popularity among NA gardeners.

But what about the other 90%? What if another variety of clematis accounts for MORE than 10% of the one million? In that case, jackmanii would not be the most popular variety at the nursery. However, if no other variety accounts for 10% (or more) of the one million, then jackmanii would be in fact be the most popular variety at the nursery.

Would that prove that jackmanii is the most popular variety in NA? Not necessarily. But if jackmanii is #1 at the largest nursery, that's certainly EVIDENCE that jackmanii is #1 in NA. Again, we are trying to conclude that the belief is APPARENTLY correct, not that the believe is DEFINITELY correct. As long as we have evidence that jackmanii is the most popular variety among NA gardeners, we're in good shape.

With that in mind, let's look at the answer choices:

Quote:
(A) The nursery sells more than 10 different varieties of clematis

If the nursery sells 10 varieties or fewer, then there would HAVE to be another variety that accounts for more than 10% of the one million plants sold at the nursery. If that were true, then jackmanii could not be the most popular variety at the nursery. Thus, we would not have evidence that jackmanii is #1 in NA. Without choice (A), the argument falls apart.

Now, does choice (A) PROVE that jackmanii is #1 at the nursery? Not at all... even with 20 varieties, there could be another type that accounts for more than 10% of the million. That, of course, would ruin the argument.

Even if choice (A) is true, the argument may or may not be valid, but that's okay. In other words, choice (A) doesn't PROVE that the author's reasoning is sound. But without choice (A), the author's argument could not be valid. This is a required assumption, so keep (A).

Quote:
(B) The largest clematis nursery in North America sells nothing but clematis plants

The nursery could sell many other types of plants. As long as jackmanii is the most popularity variety of clematis plant sold at the nursery, then the author's reasoning holds up. This is not a required assumption, so eliminate (B).

Quote:
(C) Some of the jackmanii sold by the nursery are sold to gardeners outside North America

If a substantial portion of jackmanii sales were to gardeners outside of NA, then we might have a problem. That might suggest that jackmanii's popularity at the nursery is NOT a good indicator of jackmanii's popularity among NA gardeners.

Choice (C) only says that SOME of the jackmanii are sold to gardeners outside of NA. In that case, the jackmanii sales at the nursery are probably a good indicator of its popularity among NA gardeners.

Does that make (C) a REQUIRED assumption? If (C) were not true and the nursery ONLY sold jackmanii to gardeners within NA, then that would probably further strengthen the argument. That would give us even more reason to believe that the sales at the nursery are a good indicator of NA popularity. Choice (C) is not a required assumption, so eliminate (C).

Quote:
(D) Most North American gardeners grow clematis in their gardens

It doesn't matter whether clematis is a popular plant in general. The belief is that jackmanii is the most popular variety OF clematis. Even if only a tiny fraction of NA gardeners grow clematis, jackmanii could still be the most popular variety among those gardeners who DO grow clematis. Eliminate (D).

Quote:
(E) For all nurseries in North America that specialize in clematis, at least 10% of the clematis plants they sell are jackmanii.

This is admittedly a little bit tempting: sure, it would strengthen the argument. But this isn't a strengthen question: we need to know whether this is NECESSARY to draw the conclusion.

And it isn't necessary: even if (E) is NOT true -- for example, if jackmanii accounts for less than 10% of clematis plants at a few nurseries -- it's still possible that jackmanii is the most popular. And since (E) isn't necessary, it's not the correct answer.

How the individual vine percentage figure accounts to less than 10℅ when for the case of say 11 vines are distributed like 1,1,1,1,1,1,1,1,1,81,10(jackmanii) percent..how can this case be dealt with? In this case we have the vine with 82℅ as winner...where am I missing out?
When there are 10 or less than 10 varieties,jackmanii cannot be the winner as other vines will have a starting percentage of 10 ℅ each,any change in distribution will make another vine the majority. Whereas, over 10 varieties may or may not make another vine a majority.
Do we need this
assumption --> conclusion verification in assumtion questions because this approach seem to fail here to prove 'A' as the answer...Please clear my doubt.

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Many gardeners believe that the variety of clematis vine that is most [#permalink]
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AnuragRatna wrote:
Many gardeners believe that the variety of clematis vine that is most popular among gardeners in North America is jackmanii. This belief is apparently correct since, of the one million clematis plants sold per year by the largest clematis nursery in North America, ten percent are jackmanii.

Which of the following is an assumption on which the argument depends?

(A) The nursery sells more than 10 different varieties of clematis

(B) The largest clematis nursery in North America sells nothing but clematis plants

(C) Some of the jackmanii sold by the nursery are sold to gardeners outside North America

(D) Most North American gardeners grow clematis in their gardens

(E) For all nurseries in North America that specialize in clematis, at least 10% of the clematis plants they sell are jackmanii.

Variety of Clematis vine that is MOST popular is jackmanii in NA.
This is correct since in NA, 10% of clematis plants sold are jackmanii.

We are looking for an assumption. The following things are going through my mind.

Just 10% of clematis is jackmanii but it is the most popular variety. That means no other variety accounts for 15% or 20% of clematis sold. All other varieties account for less than 10% each. So A, a variety of clematis could account for 4%, B could account for 9% etc, but none above 10%.
This certainly means that there are more than 10 varieties to make up the 100%. If there were exactly 10 varieties, the minimum that each would need to be is at 10% to make up 100% but that would mean that all are equally popular. So there MUST be more than 10 varieties and each must account for LESS THAN 10% of the total.

Also, I am thinking, that I need to compare jackmanii with other clematis varieties. Anything that compares clematis with other plants is irrelevant. Anything that compares jackmanii with other plants (other than clematis) is irrelevant.

(A) The nursery sells more than 10 different varieties of clematis

This is an assumption. It NEEDS to be true for the conclusion to hold as discussed above.

(B) The largest clematis nursery in North America sells nothing but clematis plants

Not needed. Even if they sell other plants, that is irrelevant. We need to focus on how many varieties and in what number are clematis plants sold.

(C) Some of the jackmanii sold by the nursery are sold to gardeners outside North America

We don't need this to be true. We don't need that some jackmanii should be sold outside NA.
Do we need all jackmanii to be sold within NA? Not necessary but we would consider other information in that case.

(D) Most North American gardeners grow clematis in their gardens

We don't need this to be true. Among those who grow clematis, jackmanii is the most popular. It is possible that only 2% of NA gardeners grow clematis.

(E) For all nurseries in North America that specialize in clematis, at least 10% of the clematis plants they sell are jackmanii.

No. We have data about the largest nurseries in NA. Nurseries that specialise in clematis could be just 1% of all largest nurseries with very low volume. Their numbers could be insignificant.

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Re: Many gardeners believe that the variety of clematis vine that is most [#permalink]
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Panoj wrote:
GMATNinja wrote:
The conclusion of this passage is that the gardener's belief--that jackmanii is the most popular variety of clematis vine among gardeners in North America (NA)--is apparently correct. The word "apparently" is very important here. The conclusion would be substantially different if we were to replace "apparently" with "definitely".

More on that in a moment... but first, why does the author conclude that the belief is apparently correct?

• The largest clematis nursery in NA sells one million clematis plants per year.
• Of the one million clematis plants sold per year by that nursery, ten percent are jackmanii.

A substantial chunk of the clematis plants sold at the largest nursery are jackmanii. The author reasons that jackmanii's popularity at the largest nursery is a good indicator of its popularity among NA gardeners.

But what about the other 90%? What if another variety of clematis accounts for MORE than 10% of the one million? In that case, jackmanii would not be the most popular variety at the nursery. However, if no other variety accounts for 10% (or more) of the one million, then jackmanii would be in fact be the most popular variety at the nursery.

Would that prove that jackmanii is the most popular variety in NA? Not necessarily. But if jackmanii is #1 at the largest nursery, that's certainly EVIDENCE that jackmanii is #1 in NA. Again, we are trying to conclude that the belief is APPARENTLY correct, not that the believe is DEFINITELY correct. As long as we have evidence that jackmanii is the most popular variety among NA gardeners, we're in good shape.

With that in mind, let's look at the answer choices:

Quote:
(A) The nursery sells more than 10 different varieties of clematis

If the nursery sells 10 varieties or fewer, then there would HAVE to be another variety that accounts for more than 10% of the one million plants sold at the nursery. If that were true, then jackmanii could not be the most popular variety at the nursery. Thus, we would not have evidence that jackmanii is #1 in NA. Without choice (A), the argument falls apart.

Now, does choice (A) PROVE that jackmanii is #1 at the nursery? Not at all... even with 20 varieties, there could be another type that accounts for more than 10% of the million. That, of course, would ruin the argument.

Even if choice (A) is true, the argument may or may not be valid, but that's okay. In other words, choice (A) doesn't PROVE that the author's reasoning is sound. But without choice (A), the author's argument could not be valid. This is a required assumption, so keep (A).

Quote:
(B) The largest clematis nursery in North America sells nothing but clematis plants

The nursery could sell many other types of plants. As long as jackmanii is the most popularity variety of clematis plant sold at the nursery, then the author's reasoning holds up. This is not a required assumption, so eliminate (B).

Quote:
(C) Some of the jackmanii sold by the nursery are sold to gardeners outside North America

If a substantial portion of jackmanii sales were to gardeners outside of NA, then we might have a problem. That might suggest that jackmanii's popularity at the nursery is NOT a good indicator of jackmanii's popularity among NA gardeners.

Choice (C) only says that SOME of the jackmanii are sold to gardeners outside of NA. In that case, the jackmanii sales at the nursery are probably a good indicator of its popularity among NA gardeners.

Does that make (C) a REQUIRED assumption? If (C) were not true and the nursery ONLY sold jackmanii to gardeners within NA, then that would probably further strengthen the argument. That would give us even more reason to believe that the sales at the nursery are a good indicator of NA popularity. Choice (C) is not a required assumption, so eliminate (C).

Quote:
(D) Most North American gardeners grow clematis in their gardens

It doesn't matter whether clematis is a popular plant in general. The belief is that jackmanii is the most popular variety OF clematis. Even if only a tiny fraction of NA gardeners grow clematis, jackmanii could still be the most popular variety among those gardeners who DO grow clematis. Eliminate (D).

Quote:
(E) For all nurseries in North America that specialize in clematis, at least 10% of the clematis plants they sell are jackmanii.

This is admittedly a little bit tempting: sure, it would strengthen the argument. But this isn't a strengthen question: we need to know whether this is NECESSARY to draw the conclusion.

And it isn't necessary: even if (E) is NOT true -- for example, if jackmanii accounts for less than 10% of clematis plants at a few nurseries -- it's still possible that jackmanii is the most popular. And since (E) isn't necessary, it's not the correct answer.

How the individual vine percentage figure accounts to less than 10℅ when for the case of say 11 vines are distributed like 1,1,1,1,1,1,1,1,1,81,10(jackmanii) percent..how can this case be dealt with? In this case we have the vine with 82℅ as winner...where am I missing out?
When there are 10 or less than 10 varieties,jackmanii cannot be the winner as other vines will have a starting percentage of 10 ℅ each,any change in distribution will make another vine the majority. Whereas, over 10 varieties may or may not make another vine a majority.
Do we need this
assumption --> conclusion verification in assumtion questions because this approach seem to fail here to prove 'A' as the answer...Please clear my doubt.

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Note that an assumption is a necessary condition; it need not be a sufficient condition. You NEED more than 10 varieties but just having 11 varieties may not be ENOUGH. You need to ensure that each variety other than jackmanii is less than 10%.
The question is looking for an assumption. Option (A) is a NECESSARY condition.
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Re: Many gardeners believe that the variety of clematis vine that is most [#permalink]
a.The nursery sells more than 10 different varieties of clematis

From negation, I was able to get to A.
However, this does not have to necessarily be true, does it? There can be 9 different varieties and still the conclusion will hold true.
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