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

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Intern
Joined: 09 Nov 2015
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GPA: 3.56
Re: Blood banks will shortly start to screen all donors for NANB [#permalink]

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09 Feb 2016, 20:44
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

No math is needed. The logical gap, in my opinion, is the criteria that would disqualify someone from the screening test. What if the screening test only tests for a portion of infections that are found in NANB-contaminated blood? Choice A fills that void.

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Senior Manager
Joined: 07 Sep 2014
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Concentration: Finance, Marketing
Re: Blood banks will shortly start to screen all donors for NANB [#permalink]

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13 Aug 2016, 04:32
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.

Total case 100
total cases after screening :- 95
5 they caught so 10 they will miss and that's what 10% of actual donor who will still supply NANB contaminated blood.

The argument above depends on which of the following assumotptions?

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

Negate -
Donors carrying NANB hepatitis do, in a large percentage of cases, carry other infections for which reliable screening tests are routinely performed.

so lets say these 4 are screened because of other disease. so 1 for Hepatitis.
in that case 2 they have missed. so total Hepatitis case = 3
now it should be 10 but now it is 3. Conclusion no good any more.

(C) The estimate of the number of donors who would be disqualified by tests for NANB hepatitis is an underestimate.

(E) The donors who will still supply NANB-contaminated blood will donate blood at the average frequency for all donor

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

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14 Mar 2017, 10:59
okay, i got it, the answer cannot be E because the argument mentions "% of donors", not "% of contamination"

Kudos [?]: 11 [0], given: 865

Senior Manager
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Posts: 484

Kudos [?]: 30 [0], given: 342

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

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12 Sep 2017, 04:43
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.

Total screening = 100
they will still miss two-thirds of donors carrying NANB hepatitis
so lets say total donors carrying NANB hepatitis = x
only 1/3 will be identified
2/3 will be missed.

5 percent of all prospective blood donors = 1/3 correctly identified + wrongly identified who doesn't carry NANB.

Conclusion :-
this 2/3 = 10% of actual donors who will supply NANB-contaminated blood.

100*x*2/3 = 10%
x has to be 15.

about 10 percent of actual donors will still supply NANB-contaminated blood. we have to diminish this no.

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.
Donors carrying NANB hepatitis do , in a large percentage of cases, carry other infections for which reliable screening tests are routinely performed.
if this happens than Donors carrying NANB hepatitis will be screened by some other tests and percentage would be below than what we have estimated.

(C) The estimate of the number of donors who would be disqualified by tests for NANB hepatitis is an underestimate.
5 percent of all prospective blood donors = 1/3 correctly identified + wrongly identified who doesn't carry NANB. => is an understatement. so lets say 10% will be disqualified.
just that x will change.

they will still miss two-thirds of donors carrying NANB hepatitis. :- this is still intact.

Conclusion :-
this 2/3 = 10% of actual donors who will supply NANB-contaminated blood
this no. still holds

(E) The donors who will still supply NANB-contaminated blood will donate blood at the average frequency for all donors.
This doesn't do anything to lower the percentage. It is just saying that
Frequency of donation
The donors who will still supply NANB-contaminated blood = avg frequency of all donor.
so if avg donor donates 10 times , The donors who will still supply NANB-contaminated blood will also donate 10 times.

Kudos [?]: 30 [0], given: 342

Re: Blood banks will shortly start to screen all donors for NANB   [#permalink] 12 Sep 2017, 04:43

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