Critical Reasoning

Because ethylene dibromide, a chemical used to fumigate grain, was blamed for the high rate of nerve damage suffered by people who work in grain-processing plants, many such plants switched to other chemical fumigants 2 years ago. Since then, however, the percentage of workers at these plants who were newly diagnosed with nerve damage has not dropped significantly. Therefore, either ethylene dibromide was wrongly blamed or else the new chemicals also cause nerve damage.
Which of the following is an assumption on which argument depends?

A. If the new chemicals cause nerve damage, the nerve damage caused would be different from any nerve damage that ethylene dibromide may cause.
B. There are no chemical fumigants that are completely safe for workers in grain-processing plants.
C. If ethylene dibromide causes nerve damage, it does not take 2 years or longer for that damage to become detectable.
D. Workers at grain-processing plants typically continue to work there even after being diagnosed with nerve damage.
E. Workers at grain-processing plants that still use ethylene dibromide continue to have a high rate of nere damage.

I chose C, but basically I kind of guessed.

jamesk486 wrote:Because ethylene dibromide, a chemical used to fumigate grain, was blamed for the high rate of nerve damage suffered by people who work in grain-processing plants, many such plants switched to other chemical fumigants 2 years ago. Since then, however, the percentage of workers at these plants who were newly diagnosed with nerve damage has not dropped significantly. Therefore, either ethylene dibromide was wrongly blamed or else the new chemicals also cause nerve damage.
Which of the following is an assumption on which argument depends?

A. If the new chemicals cause nerve damage, the nerve damage caused would be different from any nerve damage that ethylene dibromide may cause.
B. There are no chemical fumigants that are completely safe for workers in grain-processing plants.
C. If ethylene dibromide causes nerve damage, it does not take 2 years or longer for that damage to become detectable.
D. Workers at grain-processing plants typically continue to work there even after being diagnosed with nerve damage.
E. Workers at grain-processing plants that still use ethylene dibromide continue to have a high rate of nere damage.

I chose C, but basically I kind of guessed.

The argument basically says that the the plant switched from x to y
and that since the new cases of nerve damage hasn't changed, y
hasn't helped.

The underlying assumption is that damage caused by x can be
detected immediately. C correctly plugs this gap in the argument.

A and B are out of scope.
D does not help assumption
E just tells us what the question stem told us. No additional info.

When in doubt use the negation technique on assumption question. What you basically do is negate the assumption and see if it destroys the argument, if it does then you have the right answer and if it does not or if it helps the argument then it is a wrong answer.

Answer Choice C says:
If ethylene dibromide causes nerve damage, it does not take 2 years or longer for that damage to become detectable.

Now negate the above assumption:
If ethylene dibromide causes nerve damage, it does take 2 years or longer for that damage to become detectable.

Now clearly if it does take 2 years or longer to detect damage then clearly ethylene dibromide was correct to be blamed and the new fumigant might have nothing to do with the new cases of nerve damage. When negated this statement destroys the argument hence its the correct answer.

guynoor wrote:When in doubt use the negation technique on assumption question. What you basically do is negate the assumption and see if it destroys the argument, if it does then you have the right answer and if it does not or if it helps the argument then it is a wrong answer.

Answer Choice C says:
If ethylene dibromide causes nerve damage, it does not take 2 years or longer for that damage to become detectable.

Now negate the above assumption:
If ethylene dibromide causes nerve damage, it does take 2 years or longer for that damage to become detectable.

Now clearly if it does take 2 years or longer to detect damage then clearly ethylene dibromide was correct to be blamed and the new fumigant might have nothing to do with the new cases of nerve damage. When negated this statement destroys the argument hence its the correct answer.

Though I can make right answer based on PoE, I still fail to understand the Negation Technique(TM) Powerscore here, could u explain, if u r still alive at btg

maihuna wrote:

guynoor wrote:When in doubt use the negation technique on assumption question. What you basically do is negate the assumption and see if it destroys the argument, if it does then you have the right answer and if it does not or if it helps the argument then it is a wrong answer.

Answer Choice C says:
If ethylene dibromide causes nerve damage, it does not take 2 years or longer for that damage to become detectable.

Now negate the above assumption:
If ethylene dibromide causes nerve damage, it does take 2 years or longer for that damage to become detectable.

Now clearly if it does take 2 years or longer to detect damage then clearly ethylene dibromide was correct to be blamed and the new fumigant might have nothing to do with the new cases of nerve damage. When negated this statement destroys the argument hence its the correct answer.

Though I can make right answer based on PoE, I still fail to understand the Negation Technique(TM) <a href="https://powerscore.com/gmat/content_inde ... erScore</a> here, could u explain, if u r still alive at btg

Hi Maihuna,

I have discussed application of the Kaplan negation test (or Kaplan denial test) to several different kinds of CR questions in many of my posts. I would suggest simply going through some of my recent (or, if you want, not recent!) CR posts for some examples of denial test being applied. Alternatively, post a necessary assumption or inference question, and I can discuss application of denial test. You can also use denial test effectively in many strengthen/weaken questions (when struggling between two answer choices.)

The argument can be reduced to this paraphrase:

"Because there has not been a drop in nerve damage in the last two years using the other fumigants, there was nothing wrong with ethylene dibromide."

You should always try to reduce arguments down to: "because x, y" in your head so that it makes it easier to think about them.

Let's look at choice C, and then apply the denial test:

C. If ethylene dibromide causes nerve damage, it does not take 2 years or longer for that damage to become detectable.

So, does the argument depend on this assumption? What would happen to the argument if we removed (ie, "negated" or "denied") this assumption?

Choice C denied: If ethylene dibromide causes nerve damage, it takes longer than 2 years for the damage to become detectable.

If that's true--if it DOES take longer than two years for ethylene dibromide's damage to be detectable--then it indicates that his reason--that it's been two years using the other fumigants and there hasn't been a drop in nerve damage--no longer establishes that there was nothing wrong with ethylene dibromide: after all, it's been only two years and the fact that the incidence of nerve damage hasn't declined can easily be attributed to the fact that when ethylene dibromide causes nerve damage it takes more than two years for the damage to be detected!

So, if we remove (ie, deny or negate) choice C, then the author's argument is struck at its heart. Therefore, the argument's logical existence depends on choice C.

guynoor also does a fine job of applying the denial test, and I'm sure he ended up doing well in CR. The only remark I would make about his post involves his seond-to-last sentence: "Now clearly if it does take 2 years or longer to detect damage then clearly ethylene dibromide was correct to be blamed and the new fumigant might have nothing to do with the new cases of nerve damage."

I would change this to "Now clearly if it does take 2 years or longer to detect damage then clearly ethylene dibromide was not necessarily incorrect to be blamed and the new fumigant might have nothing to do with the new cases of nerve damage."

Great explanation TestLuv, thanks as always.

Thanks Testluv for the great explaination .

Regards,
Shobha

Because ethylene dibromide, a chemical used to fumigate grain, was blamed for the high rate of nerve damage suffered by people who work in grain-processing plants, many such plants switched to other chemical fumigants two years ago.

Since then, however, the percentage of workers at these plants who were newly diagnosed with nerve damage has not dropped significantly.

Therefore, either ethylene dibromide was wrongly blamed or
else the new chemicals also cause nerve damage.


Hi GMAT Gurus,

The conclusion in the above argument has two parts.( Bolded)

Negated version of C :
If ethylene dibromide causes nerve damage, it takes 2 years or longer for that damage to become detectable. This shatters the first part of the conclusion but does nothing to the second part.

What if we had an answer choice which presented the favorable conditions uniquely to grain processing plants that made this new chemical to react in a way to cause nerve damage. would it have been right?

I am thinking - Can GMAT presents two assumptions for two different part of the conclusion in the same argument?