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# #Top150 CR: Blood banks will shortly start to screen all donors

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MBA Section Director
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#Top150 CR: Blood banks will shortly start to screen all donors [#permalink]

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04 Dec 2015, 09:30
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42% (01:27) correct 58% (01:59) wrong based on 282 sessions

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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
[Reveal] Spoiler: OA

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Re: #Top150 CR: Blood banks will shortly start to screen all donors [#permalink]

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04 Dec 2015, 14:24
A it is.
Negate A: Donors carrying NANB hepatitis, in a large percentage of cases, carry other infections for which reliable screening tests are routinely performed.
So, now NANB donors have other other infections and we have reasons to believe that they will be caught by some other test(s). Definitely this will reduce the number, and thus, percentage of NANB donors.

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Re: #Top150 CR: Blood banks will shortly start to screen all donors [#permalink]

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05 Dec 2015, 01:15
conclusion says 10% of overall sample still carrying NANB
why because tests miss 2/3 of NANB.

we can make conclusion false. What if these tests are rejecting donors based on some other diseases.
hence assumption will be tests are rejecting donors only on NANB results. A is the answer

Please correct me if i am missing something
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Re: #Top150 CR: Blood banks will shortly start to screen all donors [#permalink]

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03 Jan 2018, 08:24
Hi,
I couldn't relate the 10% of actual donors with the 66% of Prospective donors who were passed in the new screening test.
Can you kindly explain how A is correct
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Re: #Top150 CR: Blood banks will shortly start to screen all donors [#permalink]

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04 Jan 2018, 10:24
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. -Correct. If these people have other diseases that are easily identifiable then they will be barred from blood donation.

B. Donors carrying NANB hepatitis do not, in a large percentage of cases, develop the disease themselves at any point. -Whether they develop the diseases is out of scope because having NANB virus will make them ineligible for blood donation, if caught in the test.

C. The estimate of the number of donors who would be disqualified by tests for NANB hepatitis is an underestimate. -Let it be an underestimation for we know 10% infected people will donate blood.

D. The incidence of NANB hepatitis is lower among the potential blood donors than it is in the population at large. -Out of scope

E. The donors who will still supply NANB-contaminated blood will donate blood at the average frequency for all donors -Still it doesn't clear whether 10% will donate or not.
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Re: #Top150 CR: Blood banks will shortly start to screen all donors [#permalink]

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04 Jan 2018, 13:02
"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.
"

Isn't the correct answer choice attacking the given premise. we are given that 2/3rd will be missed. How can we attack the given fact in the argument.

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 is true, our premise doesn't stand.

I was actually hoping to see the link between donors and actual donors.
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Re: #Top150 CR: Blood banks will shortly start to screen all donors [#permalink]

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04 Jan 2018, 14:43
Leo8 wrote:
"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.
"

Isn't the correct answer choice attacking the given premise. we are given that 2/3rd will be missed. How can we attack the given fact in the argument.

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 is true, our premise doesn't stand.

I was actually hoping to see the link between donors and actual donors.

Leo8 it doesn't contradict our premise. We are asked which answer strengthens the premise that 2/3 of NANB donors will not be disqualified. One thing that is necessary for this is that those 2/3 won't be disqualified for any other reason - which is exactly what A tells us.
Is this clear, or still confusing? Why do you think the premise doesn't stand?
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Re: #Top150 CR: Blood banks will shortly start to screen all donors [#permalink]

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04 Jan 2018, 15:01
souvik101990 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

Logically, we are given an assumption (the test will miss 2/3 of NANB donors) and a conclusion (2/3 of NANB donors, or 10% of all donors, will not be disqualified). But notice this assumes those infected won't be disqualified for any OTHER reason than NANB either - which is what A suggests.

By process of elimination:
A - Yes! this means if they aren't detected for NANb, they won't be detected for anything else.
B - irrelevant
C - this contradicts the argument, it doesn't underline it
D - not relevant: the stats we were given are about the potential donors, not the population at large
E - we don't know anything about the average frequency of donors, so this is just a distraction.
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Re: #Top150 CR: Blood banks will shortly start to screen all donors [#permalink]

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10 Jan 2018, 12:43
I couldnt understand the conclusion correctly. please explain
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#Top150 CR: Blood banks will shortly start to screen all donors [#permalink]

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14 Apr 2018, 08:31
hi sahilsnpt,

the way i understood this argument is,
Considering sample size of 60 people who are donating blood.
among whom 5% disqualified because they have NAMB in their blood i.e. 3 are disqualified.
Further argument says, screening misses 2/3rd means it has caught 1/3rd of NAMB cases (1/3*x=3)
i.e. Total NAMB cases are 9 and 6 are missed cases.

6 are the people who have passed the screening despite having NAMB.
So conclusion correctly says 10% of 60(Total) i.e 6 will supply contaminated blood.

We want to break this conclusion by negating options.
option A on negation says- Donors carrying NANB hepatitis carry other infections for which reliable screening tests are routinely performed.
Means out of 6 who managed to get through new screening will fail some other screening like of other blood test criteria and that number 10% (say 6) will be reduced.
And few people despite having NAMB and having passed NAMB screening will go ahead with donation.
As this reasoning breaks conclusion. It must be the right choice.
#Top150 CR: Blood banks will shortly start to screen all donors   [#permalink] 14 Apr 2018, 08:31
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