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Blood banks will shortly start to screen all donors for NANB

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Blood banks will shortly start to screen all donors for NANB [#permalink]

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Blood banks will shortly start to screen all donors for NANB hepatitis. Although the new screening tests are estimated to disqualify up to 5 percent of all prospective blood donors, they will still miss two-thirds of donors carrying NANB hepatitis. Therefore, about 10 percent of actual donors will still supply NANB-contaminated blood.

The argument above depends on which of the following assumptions?

(A) Donors carrying NANB hepatitis do not, in a large percentage of cases, carry other infections for which reliable screening tests are routinely performed.
(B) Donors carrying NANB hepatitis do not, in a large percentage of cases, develop the disease themselves at any point.
(C) The estimate of the number of donors who would be disqualified by tests for NANB hepatitis is an underestimate.
(D) The incidence of NANB hepatitis is lower among the potential blood donors than it is in the population at large.
(E) The donors who will still supply NANB-contaminated blood will donate blood at the average frequency for all donors

Kindly explain your answers..
[Reveal] Spoiler: OA
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Re: NANB hepatitis [#permalink]

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New post 14 Aug 2009, 12:51
I think the answer is A, i got this mainly as a matter of exclusion.
I can explain my thought process if my answer is correct.
Please post the correct answer
Thank you for the gud post
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Re: NANB hepatitis [#permalink]

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New post 15 Aug 2009, 07:24
i think (e).

"up to 5 percent", "about 10 percent" seem to talk about average numbers. if (e) weren't true, then there could be 20 people, or 2 people with NANB-contaminated blood out of 100.

"other infections" in (a) seems out of context for this.
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Re: NANB hepatitis [#permalink]

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New post 15 Aug 2009, 20:56
i think its A
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Re: NANB hepatitis [#permalink]

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New post 16 Aug 2009, 12:37
Hi SKG you're right... the OA is 'A'.. Kindly explain the logic that helped you choose this option..
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Re: NANB hepatitis [#permalink]

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New post 16 Aug 2009, 13:03
argument dsnt talk about other infections.....I dont think A could be the answer.....


I have a doubt between D and E......IMO D

Please let me know if someone else has the answer for this too
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Re: NANB hepatitis [#permalink]

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New post 16 Aug 2009, 17:32
A for me.
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Re: NANB hepatitis [#permalink]

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New post 16 Aug 2009, 19:28
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Tough one.

My explanation:

If NANB carries other infections which can be tested true positive (or reliable as stated in Option A), then the chance of detecting NANB will be higher. However, Option A states that this is not the case. Hence the 2/3 of NANB will still be missed and this figure (2/3) has to be taken as accurate. Thus its a necessary assumption.
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Re: NANB hepatitis [#permalink]

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Hi,

I solved this question with a different approach. I hope you will find it useful:

The premises are all seemed peculiar to me. But, I used %age and Number to solve this.

Conclusion is on ACTUAL 10% donors, which is nowhere mentioned in the argument. So, we need to look for following as per CR Bible:
1. Options which have ACTUAL keyword.
2. Options involveing %age instead of numbers, as we are given %ages only. So, choice with numbers will be Incorrect.
3. There seems to logical gaps in the argument and the author mentioned strong words to indicate that his reasoning is air-tight, which points to a DEFENDER assumption case. So, look for negative answer choices, which involve some defending language.

abhi758 wrote:
Blood banks will shortly start to screen all donors for NANB hepatitis. Although the new screening tests are estimated to disqualify up to 5 percent of all prospective blood donors, they will still miss two-thirds of donors carrying NANB hepatitis. Therefore, about 10 percent of actual donors will still supply NANB-contaminated blood.

The argument above depends on which of the following assumptions?
(A) Donors carrying NANB hepatitis do not, in a large percentage of cases, carry other infections for which reliable screening tests are routinely performed.
(B) Donors carrying NANB hepatitis do not, in a large percentage of cases, develop the disease themselves at any point. [The conclusion is not based on this assumption. It fails to meet above three conditions and not even the negation technique proves this as an ssumption. Incorrect]
(C) The estimate of the number of donors who would be disqualified by tests for NANB hepatitis is an underestimate. [It fails to meet the (2) point above. color=#FF0000]Incorrect[/color]]
(D) The incidence of NANB hepatitis is lower among the potential blood donors than it is in the population at large. [It fails to meet the (2) point above and also comparing with the population as a whole, which is irrelevent. Incorrect]
(E) The donors who will still supply NANB-contaminated blood will donate blood at the average frequency for all donors. [This is irrelevant to the conclusion. Try the negation test. The conclusion will still be intact. Incorrect]

Kindly explain your answers..

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Re: Blood banks will shortly start to screen all donors for NANB [#permalink]

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Blood banks will shortly start to screen all donors for NANB [#permalink]

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abhi758 wrote:
Blood banks will shortly start to screen all donors for NANB hepatitis. Although the new screening tests are estimated to disqualify up to 5 percent of all prospective blood donors, they will still miss two-thirds of donors carrying NANB hepatitis. Therefore, about 10 percent of actual donors will still supply NANB-contaminated blood.

The argument above depends on which of the following assumptions?

(A) Donors carrying NANB hepatitis do not, in a large percentage of cases, carry other infections for which reliable screening tests are routinely performed.
(B) Donors carrying NANB hepatitis do not, in a large percentage of cases, develop the disease themselves at any point.
(C) The estimate of the number of donors who would be disqualified by tests for NANB hepatitis is an underestimate.
(D) The incidence of NANB hepatitis is lower among the potential blood donors than it is in the population at large.
(E) The donors who will still supply NANB-contaminated blood will donate blood at the average frequency for all donors

Kindly explain your answers..


Derived 'A' through POE.

Understanding of the passage.
P1 - Screening is happening.
P2 - Able to restrict only 5% out of 15%
C1 - Still 10% of ppl r giving the contaminated blood.

Assumption made - Some issue is there bcos of transfering this contaminated blood, Hence screening is happening in all the blood donors.

B - Donors carrying NANB hepatitis do not, in a large percentage of cases, develop the disease themselves at any point. The information provided is not creating any link between the premise and conclusion. Also, if its not going to have any effect or creating any disease then why the screening is happening.
(C) The estimate of the number of donors who would be disqualified by tests for NANB hepatitis is an underestimate. - The statement has been already stated in the main Argument. Only 1/3rd was being identified.
(D) The incidence of NANB hepatitis is lower among the potential blood donors than it is in the population at large. - Complete Out of scope. Blood Donor Vs Total Population
(E) The donors who will still supply NANB-contaminated blood will donate blood at the average frequency for all donors Again its a statement or an information which no way supports the argument. Its a mere inforation. What ever frequecny they are giving it doesnt support the Conclusion made

So Finally A. A is ok with the pre assumption made during reading the argument. We are only checking for NANB, what if any other contamination is there? Through POE and pre assumption i reached A.

A is better choice among the 5.
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Re: Blood banks will shortly start to screen all donors for NANB [#permalink]

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Meaning of the question :

Let there be 100 people(all prospective blood donors) -> so 5 people will be caught in the new test.

2/3 * (people carrying nanb) = missed

therefore 1/3 * (people carrying nanb) = those that were caught = 5

therefore, people carrying nanb = 5*3 = 15

missed people = 10 (15-5) -> this is 10% of the prospective donor and the conclusion that they will still supply contaminated blood


Conclusion : 10% of actual donors will still supply NANB-contaminated blood


Now if donors carrying nanb carry other infections for which tests are routinely performed -> then the number of people carrying

nanb (with other infection) will be caught and will be less in number.

Thus, 2/3 * (people carrying nanb) -> will be less -> those missed will be less -> then we cannot claim that 10% of the donors will

still supply contaminated blood.
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Re: Blood banks will shortly start to screen all donors for NANB [#permalink]

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New post 02 Jun 2015, 12:07
Anu26 wrote:
Meaning of the question :

Let there be 100 people(all prospective blood donors) -> so 5 people will be caught in the new test.

2/3 * (people carrying nanb) = missed

therefore 1/3 * (people carrying nanb) = those that were caught = 5

therefore, people carrying nanb = 5*3 = 15

missed people = 10 (15-5) -> this is 10% of the prospective donor and the conclusion that they will still supply contaminated blood


Conclusion : 10% of actual donors will still supply NANB-contaminated blood


Now if donors carrying nanb carry other infections for which tests are routinely performed -> then the number of people carrying

nanb (with other infection) will be caught and will be less in number.

Thus, 2/3 * (people carrying nanb) -> will be less -> those missed will be less -> then we cannot claim that 10% of the donors will

still supply contaminated blood.




Thanks Anu,for putting it to the point and easy to understand.

Cheers,
Gaurav :-D
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Re: Blood banks will shortly start to screen all donors for NANB [#permalink]

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New post 07 Jun 2015, 20:26
A is the correct answer.

if Assumption= they won't be detected for other infections (A)
then Conclusion: 10% remains not detected
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Re: Blood banks will shortly start to screen all donors for NANB [#permalink]

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New post 08 Jun 2015, 06:00
Anu26 wrote:
Meaning of the question :

Let there be 100 people(all prospective blood donors) -> so 5 people will be caught in the new test.

2/3 * (people carrying nanb) = missed

therefore 1/3 * (people carrying nanb) = those that were caught = 5

therefore, people carrying nanb = 5*3 = 15

missed people = 10 (15-5) -> this is 10% of the prospective donor and the conclusion that they will still supply contaminated blood


Conclusion : 10% of actual donors will still supply NANB-contaminated blood


Now if donors carrying nanb carry other infections for which tests are routinely performed -> then the number of people carrying

nanb (with other infection) will be caught and will be less in number.

Thus, 2/3 * (people carrying nanb) -> will be less -> those missed will be less -> then we cannot claim that 10% of the donors will

still supply contaminated blood.




Agree with the calculation. A seems to be correct here. However, E cannot be eliminated just because A fits the calculations here.
Consider this:
In a town of 1000 assume 100 carry NANB. Now, assume that the NANB carrying donors do not follow the same frequency as that of normal donors.
Case 1: NANB donors donate more frequently than normal donors. Lets assume 80 out of normal donors donate blood (88.8%) and 20 out of 100 NANB donors donate blood (20/100-> 20%)
Now, according to given info, the test will eliminate 1/3 approx 7 and miss 2/3rd of 20 NANB supplying donors i.e. aprrox 13 are missed. So here, the total NANB carrying donors donating blood will be 13/93 which is way more than 10% as stated in the example.

So it has to be the case that NABN donors and normal donors donate blood at same frequency.
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Re: Blood banks will shortly start to screen all donors for NANB [#permalink]

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New post 26 Aug 2015, 22:19
[quote="abhi758"]Blood banks will shortly start to screen all donors for NANB hepatitis. Although the new screening tests are estimated to disqualify up to 5 percent of all prospective blood donors, they will still miss two-thirds of donors carrying NANB hepatitis. Therefore, about 10 percent of actual donors will still supply NANB-contaminated blood.

The argument above depends on which of the following assumptions?

(A) Donors carrying NANB hepatitis do not, in a large percentage of cases, carry other infections for which reliable screening tests are routinely performed.
(B) Donors carrying NANB hepatitis do not, in a large percentage of cases, develop the disease themselves at any point.
(C) The estimate of the number of donors who would be disqualified by tests for NANB hepatitis is an underestimate.
(D) The incidence of NANB hepatitis is lower among the potential blood donors than it is in the population at large.
(E) The donors who will still supply NANB-contaminated blood will donate blood at the average frequency for all donors

For option A to be true we also have to assume that the blood bank does not consider blood from people with other infections.Though this is true in real life this is not stated anywhere in the argument.Hence I do not agree with option A,though other options are also not true!

Kindly please explain if I am wrong.Thank You.
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Re: Blood banks will shortly start to screen all donors for NANB [#permalink]

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I initially replied (E) incorrectly. Here's the explanation of why it is (A) -

abhi758 wrote:
Blood banks will shortly start to screen all donors for NANB hepatitis. Although the new screening tests are estimated to disqualify up to 5 percent of all prospective blood donors, they will still miss two-thirds of donors carrying NANB hepatitis. Therefore, about 10 percent of actual donors will still supply NANB-contaminated blood.

Note - 5% corr. to 1/3, so 10% corr to the remaining 2/3 who have NANB and are missed in screening.

The argument above depends on which of the following assumptions?

(A) Donors carrying NANB hepatitis do not, in a large percentage of cases, carry other infections for which reliable screening tests are routinely performed.
If this were not the case, some donors with NANB who also have other infections would be disqualified by the screening for the other infection. So, the 10% figure would change. On the other hand, if a negligible % of NANB folks carry other infections, the 10% figure wouldn't change much.

(B) Donors carrying NANB hepatitis do not, in a large percentage of cases, develop the disease themselves at any point.
Whether NANB carriers develop the disease is irrelevant to their donation of blood.
(C) The estimate of the number of donors who would be disqualified by tests for NANB hepatitis is an underestimate.
This is somewhat tough. Assume it is not an underestimate. If it is an accurate estimate, the given numbers are true and this assumption is not needed. If it is an overestimate, more than 1/3rd of donors would be disqualified. So, LESS than 10% would pass through. In the first case, the assumption is not necessary. In the second case, it actively contradicts the argument.
(D) The incidence of NANB hepatitis is lower among the potential blood donors than it is in the population at large.
Irrelevant. We have statistics for NANB already. Why bother about the rest of the population?
(E) The donors who will still supply NANB-contaminated blood will donate blood at the average frequency for all donors
This is the toughest. Here, one could argue that if NANB carriers donate blood, say, 10x more frequently as compared to uninfected patients, they would cause 10x more blood contamination. HOWEVER, this would apply if the argument argued for about 10% of BLOOD CONTAMINATION. Instead, the argument argues for the percentage of DONORS THEMSELVES. Even if one NANB donor donates 10x times, he will still be counted as a single donor.
Kindly explain your answers..


Great question. Thanks for posting.
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Re: Blood banks will shortly start to screen all donors for NANB [#permalink]

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(A) Donors carrying NANB hepatitis do not, in a large percentage of cases, carry other infections for which reliable screening tests are routinely performed.


It is already explained in the passage that 2/3rd of the NANB donors will not be detected.That means the current tests available for the NANB infection is not flawless. So the only chance is that,for NANB to be detected, they should have some other infectious disease(for which a flawless test is available) which occur along with NANB so that detection of the other disease will lead to elimination of NANB donor.This is what the logic given in option A.
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Re: Blood banks will shortly start to screen all donors for NANB [#permalink]

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New post 09 Dec 2015, 09:57
abhi758 wrote:
Blood banks will shortly start to screen all donors for NANB hepatitis. Although the new screening tests are estimated to disqualify up to 5 percent of all prospective blood donors, they will still miss two-thirds of donors carrying NANB hepatitis. Therefore, about 10 percent of actual donors will still supply NANB-contaminated blood.

The argument above depends on which of the following assumptions?

(A) Donors carrying NANB hepatitis do not, in a large percentage of cases, carry other infections for which reliable screening tests are routinely performed.
(B) Donors carrying NANB hepatitis do not, in a large percentage of cases, develop the disease themselves at any point.
(C) The estimate of the number of donors who would be disqualified by tests for NANB hepatitis is an underestimate.
(D) The incidence of NANB hepatitis is lower among the potential blood donors than it is in the population at large.
(E) The donors who will still supply NANB-contaminated blood will donate blood at the average frequency for all donors

Kindly explain your answers..

Since no answer choices directly addresses a link between 10 percent and two third in order to build a bridge over a hole, we have to depend on defender role, which is to cancel out other possibilities to negatively affect the conclusion. Only answer A is a cancelling out other possibility that can undermine the conclusion.
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Re: Blood banks will shortly start to screen all donors for NANB [#permalink]

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New post 27 Dec 2015, 21:42
data given :
1. Blood donors will be screened for NANB Hepatitis
2. New screening test will disqualify 5% of people.
3. And 2/3 of Donors will still carry NANB hepatitis (means 2/3 are missed with the test)

Conclusion : 10% of the Donors still give NANB contaminated blood.

Analysis :

5% of Donors disqualify (means correctly detected and disqualified with the screening test) and 2/3 will be missed with the test (so 1/3 are correctly tested).
The argument concludes as 10% still give contaminated blood means 2/3 corresponds to 10%,

2/3 ==> 10
1 ==> ?

(2/3)/1 = (10/x)
x= (10 * 3)/2 == 15%

so total is 15% and out out which 5% are disqualified.

How the assumption is arrvived :
Argument says Donors shall be screened for NANB Hepatitis and conclusion says 10% of them give NANB contaminated blood,
So NANB conatminated donors should only have NANB Hepatitis (no other infections of NANB) and Option A gives that info.
Re: Blood banks will shortly start to screen all donors for NANB   [#permalink] 27 Dec 2015, 21:42

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