Q15 - A certain experimental fungicide

[ali.charania]

Could someone please walk me through this question and explain why E is the correct answer and why the others fail to measure up?

Thanks.

[noah]

This is a necessary assumption question.

The conclusion is that a fungicide, when diluted, can eliminate a certain mildew from rose plants without harming other plants.

How is this known (what's the premise)? We know that the fungicide, when diluted is safe for other plants, and we know that the fungicide is effective in eliminating the mildew.

So, what's the problem? Well, does diluting the fungicide make it not as effective? We need to assume, as (E) states, that the fungicide doesn't depend on being more concentrated than the level of dilution needed to render it safe for other plants.

(A) is about other methods - out of scope.

(B) is about harming things other than plants - out of scope.

(C) is about other forms of mildew - out of scope.

(D) is tempting, however it's irrelevant since we know that the fungicide in question does eliminate the mildew completely.

That clear it up?

[gplaya123]

I just have a quick question.

Necessary assumption questions often present new information in the conclusion that creates a gap in logic.

When I read the conclusion, I thought the last part of conclusion which is "involves no risk of harming the plants" was the new information. Because the stimulus didn't talk whether the fungicide could actually pose threats to the rose.

So, I anticipated that the answer would say something like "the fungicide would not eliminate any bugs or substances that might be beneficial to the rose," and Voila, B came to close my anticipation.
I know B says harming people and all that, but could someone explain why my anticipation was wrong?

Also, I just don't understand the logic behind the answer.
I mean who knows? There could be a substance that could be stronger when diluted.
Diluting = weaker seems to be a far-fetched concept here...
I truly believe that the negation test is the sole method that one could use to get this question right.

[Kurst]

I just have a quick question.

Necessary assumption questions often present new information in the conclusion that creates a gap in logic.

When I read the conclusion, I thought the last part of conclusion which is "involves no risk of harming the plants" was the new information. Because the stimulus didn't talk whether the fungicide could actually pose threats to the rose.

So, I anticipated that the answer would say something like "the fungicide would not eliminate any bugs or substances that might be beneficial to the rose," and Voila, B came to close my anticipation.
I know B says harming people and all that, but could someone explain why my anticipation was wrong?

Also, I just don't understand the logic behind the answer.
I mean who knows? There could be a substance that could be stronger when diluted.
Diluting = weaker seems to be a far-fetched concept here...
I truly believe that the negation test is the sole method that one could use to get this question right.

Great question! I really appreciate that you explained your thinking -- it makes it a much more interesting conversation.

Anyway, I think what you can learn from this is that your anticipation was too pointed. You need to switch to wrong-to-right after you're done thinking about the gap.

Also, the stimulus states that the fungicide causes no harm to garden plants, and while your thinking about the fungicide killing something that helps plants is very LSAT-like, it would depend on the statement about the fungicide's safety to be more limited, thus leaving that wiggle room (something like, does not burn the plant).

As for (E), you may be downplaying the part of the conclusion which states that the fungicide is effective. That's only based on the general statement that it is effective, but we don't know at what concentration levels. If the effectiveness depends on it being more concentrated than is safe, than we can't both say it's effective and safe at the same time.

You may be right that you need to use the negation test here, and perhaps this means you should do a bit more formal use of the negation with this question type until it becomes more ingrained in your thinking. Probably some folks would get to (E) by eliminating (A)-(D), but confirming (E) requires either the negation test, or negation-test-like thinking

Tell me if that doesn't clear it up.

[WaltGrace1983]

Here is another way to approach this question. When I did this question the first time, I honestly didn't see the gap. I picked (E) because it "clicked" after I saw it. The main thing to recognize in this question is that it uses 2 premises and these premises talk about 2 very different things: (1) being not harmful and (2) being effective. They are in no way the same thing. Then, it uses these two premises to draw a conclusion from both premises. Check it out:

Fungicide causes no harm to garden plants only if diluted to 10 parts water / 1 part fungicide
+
Fungicide is effective; it can even eliminate the mildew from roses completely
→
As long as it is sufficiently diluted, the fungicide can both provide a means of eliminating mildew while concurrently having "no risk" of harming the plants.

*Note: the premises go from talking about "garden plants" to "rose plants." This jump is not that big of a deal because "rose plants" are "garden plants" and "garden plants" encompass "rose plants." If you are concerned about this gap, think about the first premise in this way:

Fungicide not diluted enough → Causes at least some harm to garden plants (this includes rose plants)




The assumption here is that what makes the fungicide effective does not also make it harmful. By the same token, begin not harmful does not preclude the fungicide from being effective. This is obviously a very hard gap to see in the heat of the moment but looking at the answer choices may help you as much as it helped me.

(A) Any "alternative methods" do not matter. We are talking about one method; only one. The conclusion is about "this fungicide" and how it provides a means to do X and Y.

(B) I can totally see where the above poster was going with this answer: suppose that it harmed the insects and this means that did pose some risk to harming the plants. However, this would require another assumption that roses actually have such insects that they need. This is not talked about in the stimulus so this is ultimately not necessary to think about. In addition, we of course don't need to conclude anything about if it harms people or animals. They are not included in the discussion because all we know is that it does not harm plants.

(C) We don't need to assume this. There could be a million other different infections but we are talking only about fungicide and what it does.

(D) This, in my opinion, is the hardest elimination. However, we can appeal to the word must here and realize that something may be fishy with it. This is saying: "effective → eliminate the powdery mildew." However, does this have to be true? No. The premises tell us that the fungicide merely has the "capacity to eliminate it completely." It can still presumably be effective even without eliminating it completely. Notice how the conclusion says nothing about the fungicide being effective, it just talks about it being able to eliminate the powdery mildew.

(E) The key phrase in the conclusion is "sufficiently diluted." What if "sufficiently diluting it," perhaps meaning having 100 parts water and only 1 part fungicide , would not be able to be effective? (E) shields the conclusion from this attack. This answer choice basically says that the fungicide can still be effective, even if it is sufficiently diluted.

[roflcoptersoisoi]

Premise: Fungicide provides no damage to plants only if it is diluted to ten parts waters and one part fungicide.
Premise: Fungicide is known to be so effective against powdery mildew that it can completely eliminate from rose plants

Conclusion: Fungicide as long as it is sufficiently diluted can eliminate powdery mildew from plants without providing harm to them.

GAP: Presupposes that fungicide is still effective in eliminating powdery mildew even when diluted.
Perhaps when it is diluted it loses it's potency and effectiveness.

(A) This has absolutely no bearing on the argument an definitely isn't necessary. It need not be the case that the fungicide is the only way to effectively eliminate the mildew without harming plants in order for the conclusion to be true.
(B) Out of scope. Insofar as this argument is concerned we don't care about whether or not the fungicide harms people, insects or other plants
(C) Again, not necessary to the argument. This just gives us more information about one of the premises.
(D) We're already told that the fungicide is so effective that it is able to completely neutralizes the powdery mildew. This answer choice just boosts the premise.
(E) Bingo. This is the assumption that I pointed out earlier.