In testing for food allergies, a false positive result occurs when a

Question

Which of the following best completes the passage below:

In testing for food allergies, a false positive result occurs when a person is said to be allergic to a particular food when, in fact, they are not allergic to that food. A false negative result indicates that a person is not allergic to the food when, in fact, they are. To most accurately determine food allergies, a physician should use the test that gives the smallest percentage of false negative results because ______________________.

(A) Some food allergies cause reactions severe enough to be life-threatening.

(B) None of the tests for food allergies have lasting side effects.

(C) In diagnosing food allergies it is important to be as thorough as possible, since most people with one known food allergy have other undiscovered food allergies.

(D) The proportion of tests that do not provide a clear result is the same for all tests of food allergies.

(E) All tests for food allergies have the same proportion of false positive results.

Show SpoilerOA & Explanation

Answer is E

This question illustrates a couple of critical concepts for Critical Reasoning. First it introduces you to the "Best Completes the Passage" format, in which you need to infer the question stem from the language immediately preceding the underlined portion-to-be-completed. Here that word is "because", which seeks evidence for a conclusion. And that conclusion is "in order to most accurately determine food allergies, doctors should use the test with the smallest percentage of false negatives". The goal in this question is clearly to strengthen that conclusion.

With this in mind, you are now set up for another common trap- one in which the author of the question knows where your mind wants to go, and baits you in that direction. When you think of an allergy (or really any medical) diagnosis, what is your biggest fear? Probably that the doctor will miss a diagnosis and allow you to continue with a risky behavior that could negatively affect your quality of life. Say, for example, that you are allergic to peanuts, but your doctor falsely (false negative) says that you're not. Your next peanut butter sandwich could be catastrophic! On the flip side, if the doctor tells you that you are allergic to peanuts when it turns out you're not, that's more of an inconvenience than anything. It's a bummer to not enjoy Reese's peanut butter cups, but it's not life-threatening.

So, naturally, your mind wants to minimize false negatives, to err on the side of safety. But what's the conclusion? To most accurately (not most safely!) determine allergies, you should eliminate false negatives. For this specific objective, false positives are just as detrimental as false negatives – each is inaccurate. And so the correct answer needs to give you some reason why you are only focusing on false negatives if the goal is accuracy. Choice E, which does not bear on safety (but neither does the conclusion) is correct, as it shows that false positives will be the same for each test, so the only way to become more accurate is to minimize false negatives.

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Show Answer

Official Answer

E

bb · Accepted Answer

Winner:    geno5

Official Explanation:   Answer is E

This question illustrates a couple of critical concepts for Critical Reasoning. First it introduces you to the "Best Completes the Passage" format, in which you need to infer the question stem from the language immediately preceding the underlined portion-to-be-completed. Here that word is "because", which seeks evidence for a conclusion. And that conclusion is "in order to most accurately determine food allergies, doctors should use the test with the smallest percentage of false negatives". The goal in this question is clearly to strengthen that conclusion.

With this in mind, you are now set up for another common trap- one in which the author of the question knows where your mind wants to go, and baits you in that direction. When you think of an allergy (or really any medical) diagnosis, what is your biggest fear? Probably that the doctor will miss a diagnosis and allow you to continue with a risky behavior that could negatively affect your quality of life. Say, for example, that you are allergic to peanuts, but your doctor falsely (false negative) says that you're not. Your next peanut butter sandwich could be catastrophic! On the flip side, if the doctor tells you that you are allergic to peanuts when it turns out you're not, that's more of an inconvenience than anything. It's a bummer to not enjoy Reese's peanut butter cups, but it's not life-threatening.

So, naturally, your mind wants to minimize false negatives, to err on the side of safety. But what's the conclusion? To most accurately (not most safely!) determine allergies, you should eliminate false negatives. For this specific objective, false positives are just as detrimental as false negatives – each is inaccurate. And so the correct answer needs to give you some reason why you are only focusing on false negatives if the goal is accuracy. Choice E, which does not bear on safety (but neither does the conclusion) is correct, as it shows that false positives will be the same for each test, so the only way to become more accurate is to minimize false negatives.

IanStewart · Answer

In all CR questions like this, which recommend a certain 'policy' or 'approach', you must very clearly identify the goal of that policy or approach. The question says: " To most accurately determine food allergies  a physician should use the test that gives the smallest percentage of false negative results." The red bit is all we care about in this question: using the test that is the most accurate. Any answer choice that is not about test accuracy is definitely wrong.

Using the test with the fewest false negatives sounds good if we want an accurate test, but what if that test has a lot of false positives? Then it might not be the most accurate test. But if all tests have the same proportion of false positives, the test with the fewest false negatives is the most accurate, which is why E is the correct answer.

geno5 · Answer

WINNING ANSWER!!!!
CONGRATULATIONS. YOU WIN YOURSELF A SHINY NEW VERITAS FLAGSHIP PREP COURSE.

E.
A. Irrelevant
B. Irrelevant
C. It may be important but we dont know they have other allergiees
D. If it were the same why would it matter.

igloo · Answer

Correct answer is E.

Goal -> To accurately determine food allergies

Plan -> physician must choose a test that gives a smallest % of false negative results.

Conclusion -> To achieve our goal, we must implement the above mentioned plan.

Conclusion indicates accurate determination of food allergies has something to do with false negative results.That is , it is not depending on false positive results.

As per the scope of the argument -> food allergy test may depend on false positive and false negative results and not on any other results.

Any statement, that confirms false positive results are not used/ need not be considered & only false negative reports are used to achieve the goal (to accurately determine food allergies) is the correct answer.

a. Talks abouts effects of food allergies, we require something about false negative results and how they can help in accurately determining the food allergy . Hence it doesnot effect the conclusion.

b. Here too, we are not concerned with the side effects of tests. This does not help us in accurately determining food allergy.Hence it doesnot effect the conclusion

d. proportion of unclear results doesnot give us any info about false poitive or false negative results. Without those, we cannot accurately determine the food allergies.

c. May be ! lets see in detail

This answer choice if taken as true means, most people have undiscovered allergies, so they are not aware of some of their own undiscovered allergies and hence may say they are not allergic to a particular food, where as they actually are allergic to that food. So they generate a false negative result. Most people are not aware of their own undiscovered allergies, so most people generate High number of false negative reports. But the answe choice says "It is important to be thorough" , so if people have information about their undiscovered allergies, they will not generate a false negative report. Seems good !

But wait, does it tell anything about " false postive results are not required / not considered " No !

we are left out E -> So, E is the correct answer !. Lets see how !

Tests consist of only flase positive and false negative results as per the argument. The answer choice says false positive results are constant across all tests. This means only false negatives help in determining the accuracy !.

Now say we have test 1 and test 2

test 1 - 10 false positive results and 3 false negative results
test 2 - 10 false positive results (since false positive result remain constant) and 7 false negative results.

Clearly test2 has low num of false negative results and more accurately determines the food allergy ! This supports our conclusion !

We can confirm this by negations .

Not all tests for food allergies have same proportions of false positive results. This means determining the accuracy of food allergy depends on both false positive and negative results. This breaks our conclusion which says accuracy depends only on false negative results. Since it breaks the conclusion on negation, this is the correct answer !

yashii9 · Answer

Answer E.
the premise -

1. Every type of Food allergy tests result in --> false positive & false negative

the conclusion - 
2. A test with low of false negative % should be selected.

Reasoning -

Each test has two types of result sets (false +ve & false -ve ) and hence choosing the test will be based on the ratio of both the results. As the conclusion only talks about false negative we can not conclude whether the test with low false -ve is the best or not until we know the proportion of false +ve.

Or else - if we know that all tests will give the same % of False +ve then we can conclude that the test with low false -ve should be chosen.

lets see what each answer choice say-

(A) Some food allergies cause reactions severe enough to be life-threatening. -  There is no mention of life-threat in the premise / Out of scope

(B) None of the tests for food allergies have lasting side effects. -  There is no mention of duration of side effects / Out of scope

(C) In diagnosing food allergies it is important to be as thorough as possible, since most people with one known food allergy have other undiscovered food allergies. -  no mention of other food allergies in the premise / out of scope

(D) The proportion of tests that do not provide a clear result is the same for all tests of food allergies. -  there is no mention of in conclusive results / Out of scope

(E) All tests for food allergies have the same proportion of false positive results. -  Best answer

geno5 · Answer

Thanks, BB and Veritas Gmatclub is great! Do not know what I would do without it! Good luck to todays contestants.

bb · Answer

Congratulations Geno5!

P.S. This question winner was determined by one of the Verbal Moderators, souvik101990, and I can tell you he did put a lot of thinking into the decision and so did I. Your victory is well deserved - Kudos for your perseverance. You have come very close on many questions and it is great to see you win.

Good Luck!

BIGBULL · Answer

In testing for food allergies, a false positive result occurs when a person is said to be allergic to a particular food when, in fact, they are not allergic to that food. A false negative result indicates that a person is not allergic to the food when, in fact, they are. To most accurately determine food allergies, a physician should use the test that gives the smallest percentage of false negative results.

Which of the following, if true, most supports the recommendation that is given above?

A. Some food allergies cause reactions severe enough to be life-threatening.
- not interested in the severities of "some" food allergies.

B. None of the tests for food allergies have lasting side effects.
- not interested in the side effects of food allergies

C. In diagnosing food allergies it is important to be as thorough as possible, since most people with one known food allergy have other undiscovered food allergies.
- not interested in "other undiscovered" food allergies people may have

D. The proportion of tests that do not provide a clear result is the same for all tests of food allergies
- how many different types of tests are we considering? plus, "clear result" is a little confusing -- why not just mention "a result"?

E. All tests for food allergies have the same proportion of false positive results
- correct as is. this would help us accurately determine food allergies.

Key: POE to easily elim A, B & C. Then you have to scrap it up between D & E.
> Helpful hint: reframe what the Conclusion is and what your goal is. You want to ACCURATELY determine a #. Anything that does not align with this is not addressing the Conclusion.

Kudos please if helpful

semwal · Answer

To most accurately determine food allergies, a physician should use the test that gives the smallest percentage of false negative results because _________________________

THE MOST ACCURATE TEST WILL BE - MIN false positive( X) + MIN false negative( Y)

X + Y has to be minimum......
If Y IS CONSTANT ie MIN false negative( Y) is constant ..........
The best test ie best min error test will be one which has MINIMUM X ie MIN false positive( X)

HENCE ANSWER IS (E)...
E. all tests for food allergies have the same proportion of false positive results....

REGARDS and Happy New Year to all GMAT CLUBBERS.......

nailin16 · Answer

Why is it E and not A?
Please elaborate

Posted from my mobile device

urhowig · Answer

Between E & A , E is a shell game. It seems to be the right answer , but it is not.

Let me break down the argument.

Tests for allergies have 2 problems (errors)
1. False  positive , which means the person is  not allergic  , but the test shows  positive result .
2. False  negative , which means the person is  allergic  , but the test shows  negative results  .

The conclusion says that, in order to determine food allergy , the doctor must depend on the 2nd point above.

A. some food allergies cause reactions severe enough to be life-threatening
- If some food allergies can become life-threatening, does that help to prove the conclusion . No, because the severity of the food allergy is simply out of scope of this argument.

E. all tests for food allergies have the same proportion of false positive results
- If there are two types of error of the test as stated above, and the percentage of errors of type 1 are same across all the test cases, then then type 2 is the determining factor.
Let's say for all the test cases 100 = 78 gives the right results + errors (22)
We know errors are of 2 types. As the percentage of one type of error is always same, the other type (2) becomes the determining factor.

This is quite a detailed analysis , which is not possible during the actual exam. I wrote all these only to make you understand. 
Instead I relied more on negating the options out of A & E. Carefully reading the argument shows that A is out of scope.

VeritasPrepBrian · Answer

There are some great explanations on here for why E is correct, so kudos to everyone who has posted on that!

And then to fully answer the recurring of question of "why is it E  and not A ?" let me throw this out:

When you're working with a plan/strategy problem (as opposed to a classic "argument"), the goal/objective plays the role of the conclusion. And as always with Strengthen/Weaken, the specific conclusion is absolutely crucial! The same, then, is true of the objective. Here, look at what the objective is:

"To  most accurately  determine food allergies."

Choice A doesn't tell you why focusing on false negatives leads to increased  accuracy . Choice A is all about safety/severity - it supports a different conclusion/objective, to be as safe as possible. Which...I like telling my classes when we do this one (and at least half of people pick A every time), if you pick A, you're a really good person and will be a really good parent. Of course any good person would want to minimize the number of false negatives, because if someone thinks that they're not allergic but it turns out that they are, then they may very well eat something that could seriously hurt or even kill them. So you should absolutely in your heart and soul want to pick A for humanitarian reasons...but the goal as stated in the argument isn't safety, it's accuracy. And if the tests that reduce false negatives by 1%, in turn, increase false positives by 50%, then you haven't prioritized accuracy.

So that's the problem with A. It:

-Doesn't deal with the specific conclusion/objective, so it's incorrect.

-Is really tempting because the objective it leads to is one that your mind should naturally gravitate toward.

-Teaches a great lesson. The precise language in the conclusion (or objective) is absolutely crucial, so make sure that you read it carefully.

One more note on A - we like to call the device behind A "selling the wrong answer" through "mental inertia." If you have an interest in or some knowledge of a CR topic, it's even more important to be extra careful when reading the prompt/conclusion/objective because on those topics it's easier for the testmaker to satisfy that "ah, I like this answer" reaction with a wrong answer, because what it's satisfying is more related to your opinion or recollection. So if the topic matter speaks to you, remind yourself to slow down just a bit more so that you don't chase an answer that "feels good" but doesn't directly answer the question.

IanStewart · Answer

This question is almost an exact copy of an old OG question:

https://gmatclub.com/forum/in-tests-for ... 37758.html

The official version would be the more worthwhile one to study, if only because it is better written.

LakerFan24 · Answer

In testing for food allergies, a false positive result occurs when a person is said to be allergic to a particular food when, in fact, they are not allergic to that food. A false negative result indicates that a person is not allergic to the food when, in fact, they are. To most accurately determine food allergies, a physician should use the test that gives the smallest percentage of false negative results.

Which of the following, if true, most supports the recommendation that is given above?

A. Some food allergies cause reactions severe enough to be life-threatening.
- not interested in the severities of "some" food allergies.

B. None of the tests for food allergies have lasting side effects.
- not interested in the side effects of food allergies

C. In diagnosing food allergies it is important to be as thorough as possible, since most people with one known food allergy have other undiscovered food allergies.
- not interested in "other undiscovered" food allergies people may have

D. The proportion of tests that do not provide a clear result is the same for all tests of food allergies
- how many different types of tests are we considering? plus, "clear result" is a little confusing -- why not just mention "a result"?

E. All tests for food allergies have the same proportion of false positive results
- correct as is. this would help us accurately determine food allergies.

Key: POE to easily elim A, B & C. Then you have to scrap it up between D & E.
> Helpful hint: reframe what the Conclusion is and what your goal is. You want to ACCURATELY determine a #. Anything that does not align with this is not addressing the Conclusion.

Kudos please if helpful

kornn · Answer

Dear  VeritasKarishma ,

Does choice D. talk about inconclusive results - NOT providing both false negatives and positives ?

(D) The proportion of tests that do  not provide a clear result  is the same for all tests of food allergies.

Thank you!

KarishmaB · Answer

Yes, inconclusive result means it gives neither a positive nor a negative.

The argument gives two ways in which test results can misdirect people - false positive or false negative. Then the argument says that we should worry about the false negative because ... 
So basically it says that we should ignore the false positive measure. Hence the sentence that completes it should say why we should ignore the false positive measure. 
The argument doesn't talk about "inconclusive result" so it wouldn't be the reason for using just the false negative measure.
Also, "inconclusive result" is not misdirection, perhaps a wastage of time and money but certainly not that serious.

VerbalBot · Answer

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In testing for food allergies, a false positive result occurs when a

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GMAT Critical Reasoning (CR) Questions

In testing for food allergies, a false positive result occurs when a

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