Critical Reasoning

In tests for pironoma, a serious disease, a false positive result indicates that people have pironoma when, in
fact, they do not; a false negative result indicates that people do not have pironoma when, in fact, they do. To
detect pironoma most accurately, physicians should use the laboratory test that has the lowest proportion of
false positive results.
Which of the following, if true, gives the most support to the recommendation above?
(A) The accepted treatment for pironoma does not have damaging side effects.
(B) The laboratory test that has the lowest proportion of false positive results causes the same minor side
effects as do the other laboratory tests used to detect pironoma.
(C) In treating pironoma patients, it is essential to begin treatment as early as possible, since even a week of
delay can result in loss of life.
(D) The proportion of inconclusive test results is equal for all laboratory tests used to detect pironoma.
(E) All laboratory tests to detect pironoma have the same proportion of false negative results.

Can someone please explain the above CR?

Both false positive and false negative are evil, and we might have to live with them till the test procedure becomes more accurate....
Now we have to see which one is more harmful, and thus avoid it....

False positive can be harmful, as you are giving medicines when not required, thus causing unnecessary side-effects.
False negative can be harmful, as the patient will go untreated for the disease...

In the argument it is stated that we should avoid false positive results (assuming them to be more harmful) Thus we are looking for an answer that makes the assumption clear...

(a) weakens the conclusion...
(b) weakens the conclusion...
(c) weakens the conclusion...
(d) out of scope...
(e) this statement lends some support... as false negative cases can not be used to distinguish laboratories, false positive should be used to differentiate the laboratories...

Awsome!!! Thank you.

Great explanation! Thanks.

Why not "A". If the treatment has no damaging side effect then people misdiagnosed of having pironoma (false positive cases) might get treated for it without any side effect.

swapniltripathi -

The reason that A is not corrrect is that the conclusion has nothing to do with negative effects or the test that would be the best for patient, or anything else.

The conclusion is: "To detect pironoma most accurately, physicians should use the laboratory test that has the lowest proportion of false positive results."

So you see what this is really saying is that "the most accurate test is the one that has the lowest proportion of false positives." This is a strengthen question, so you are looking for the answer choice that makes it true that the test with the lowest false positives is the most accurate.

The conclusion that the test with the lowest proportion of false positives is the most accurate - the conclusion does not assume that the positive tests are more harmful. It has nothing to say on this, just that the most accurate test has the fewest false positives.

Now there are two ways to be inaccurate - false negative and false positive. The argument then makes the unsupported conclusion that the fewest false positives is the most accurate. Now we need to make this conclusion true. If you eliminate the false negatives as a possible error then false positives are all you have left.

Hope that helps!

In tests for pironoma, a serious disease, a false positive result indicates that people have pironoma when, in
fact, they do not; a false negative result indicates that people do not have pironoma when, in fact, they do.

Recommendation:
To detect pironoma most accurately, physicians should use the laboratory test that has the lowest proportion of
false positive results.

Take away from the recommendation and the below equation:

As false positive means actually there is no disease.


a false +ve = Says YES = Actually NO
a false -ve = Says NO = Actually YES




Which of the following, if true, gives the most support to the recommendation above?


(A) The accepted treatment for pironoma does not have damaging side effects.

Nothing is given about any damaging effects, this is out of scope - we are just talking about of +ve and -ve tests, and how to deal with it.

(B) The laboratory test that has the lowest proportion of false positive results causes the same minor side
effects as do the other laboratory tests used to detect pironoma.

Very important - the subject is deviated from the original Stance, from the testing methodologies to the minor side effects, nowhere in the passage , side effects are mentioned. VERY Out of Context

(C) In treating pironoma patients, it is essential to begin treatment as early as possible, since even a week of
delay can result in loss of life.

Can result in loss of life - firstly this is out of scope of the recommendation, how easily this option is deviating from the test results to - already disease leading to loss in life.
WAy out of scope

(D) The proportion of inconclusive test results is equal for all laboratory tests used to detect pironoma.

The stance has nothing to do with "inconclusive test" - its total deviation from the main point.

(E) All laboratory tests to detect pironoma have the same proportion of false negative results.

Finally, we have an option that talks about - laboratory tests...

WHY FALSE POSITIVE is recommended ?

Now - looking at the below equation....

Guess, for an instance false negative results were extreme and varying values...all other calculations will change, and this will inverse , indeed weaken the recommendation....of using false positive ?


Think it as a graphical representation.....if we have to see the correct bar graph....than what is not recommended has to be linear...than only we can tap the non-nonsensical behavior of the other....

The same proportion of false negative results - this resonates to be a linear representation ....and
a false +ve fluctuates ...



a false +ve = Says YES = Actually NO
a false -ve = Says NO = Actually YES

If, it was given about weakening the recommendation ,

the examiner is sure shot - to have something like this....

(E) All laboratory tests to detect pironoma have the varying proportion of false negative results.

Hope, this helps....

Guys,

I agree with the answer but can someone explain how choosing False positive lab = lowest proportion of False positive lab?

Vidhya

A lot of CR stats. problem takes a little bit of math to see what's going on in the problem, best way to tackle them is to express them in equation.

Essentially, the condition is that we're comparing a bunch of tests, which consist of:

false positve + false negative

The numbers for this is the same for all tests.

The equation is basically as follow:

(false positive/the sum of false positive and false negative, which is the total number of tests) + (false negative/the sum of false positve and false negative) = the sum of false positve + false negative/the sum of false positive and false negative or equals 1.

The last part is the same for all the tests.

If the determining factor is the first part of this equation, which is the proportion of false positive, or false positive/the sum of false positive and false negative, then we have to make sure the second part is the same to begin with.

The second part, as I've shown, false negative/the sum of false positve and false negative, is the same thing as proportion of false negative.

in other words, if you're comparing different equations of A+B=C
if you are saying that A makes all the difference in those cases, then B and C must be the same for all cases.

Thanks for the explanation provided.

False +ive Report = No Disease
False -ive Negative Report = Disease

So both the false need to be congruent for the Conclusion to be accurate
(A) Weaken--Supports the False Report as true
(B) Weaken--Establishes the false test as true test
(C) Out Of scope
(D) Out Of Scope
(E) CORRECT