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

The problem with (A) is that the argument does not give us enough information to deduce that.

10% of actual donors will supply NANB contaminated blood. But does that mean that all this blood will be used? What if actually only 50% of the blood from a blood bank is used. Then the actual incidence of disease may increase by only 5% (assuming homogenous distribution).
Also, what if NANB infected people are the ones who need blood most often from blood banks. In that case, we may find very few new cases.
Hence, increase in the incidence of disease is a big jump.

(D) is straight forward. 5% fewer people will be able to donate blood due to new tests and that means reduced supply is an effect of the new test.
In inference questions, simpler is usually better.

For discussions on assumption questions, check my blog:
https://anaprep.com/?s=assumption
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AjiteshArun ChiranjeevSingh VeritasKarishma aragonn
As per the question
Let's assume there are 100 people who donate blood
now 15 have NANB hepatitis 5 are removed from the screening. So 10 are left
Conclusion: Therefore, about 10 percent of actual donors will still supply NANB-contaminated blood.
It means the 5 people which are removed are replaced by new donors free from NANB hepatits
So how can we inder D ? since the donors remain the same
What's the flaw in my reasoning ?

There is a problem in the highlighted sentence. How do you figure that they will be replaced by new donors? The argument says "5 percent of all prospective blood donors will be disqualified"
From where will the new donors come?
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Hi Experts,

I have doubt on D.

Can we readily assume that there will no significantly more people that would like to donate blood?
If it is not the case, the blood supply can still increase.

Please explain.

Thank you.

The question states, "Which of the following inferences about the consequences of instituting the new tests is best supported by the passage above?" So we don't need to PROVE that (D) is true; as long as the information in the passage supports (D) more than any other choice, we've found our winner. And by POE, we can see that (D) is the best bet.

Also, notice the wording of (D) itself: "The blood supplies available from blood banks are likely to go down." (D) does not say the blood supplies will DEFINITELY go down. The passage suggests that blood supplies will probably go down, so (D) is spot on.

I hope that helps!
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A) The incidence of new cases of NANB hepatitis is likely to go up by 10 percent.
Relationship between donors with NANB and cases isn't given; May be 10 % is utilized by 2%?; Eliminate

B) Donations made by patients specifically for their own use are likely to become less frequent.
Irrelevant; Eliminate

C) The demand for blood from blood banks is likely to fluctuate more strongly.
Fluctuate means go up, down or both. While the demand can go up due to shortage caused by disqualification of 5% donors, other options can't be consequences of the new test. Eliminate.

D) The blood supplies available from blood banks are likely to go down.
Solid option, if the donors go down, then the supplies will go down. Hold.

E) The number of prospective first-time donors is likely to go up by 5 percent.
Goes too far; Eliminate.

D wins!­

@e gmat
would you pls help I can't understand at all

Hey nazii,

I can help with this one!

This is a question that really tests us on our ability to visualize sentences (this is particularly true of the answer choices!).

Here is a video I made that may help provide clarity.


Hope this helps!
Harsha
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I appreciate you billion times
It was very helpful
it is the best explanation ever on this question
I love egmat

Inference-based question - so let's jump to the option elimination -

A) The incidence of new cases of NANB hepatitis is likely to go up by 10 percent. - We don't know. How about if earlier, all these 15% were donating, but now the 5% are filtered at the source, so the cases should actually go down? So, it may or may not be true. Such options are not true on Inference.

B) Donations made by patients specifically for their own use are likely to become less frequent. - Is there anything like this mentioned in the passage (In inference questions no new information please, we have to stick to the argument). Out of scope.

C) The demand for blood from blood banks is likely to fluctuate more strongly. - We don't know. The argument just talks about the supply side of the equation. Anything mentioned on the demand side? No. Out of scope.

D) The blood supplies available from blood banks are likely to go down. - Perfect. Earlier suppose 100 blood brackets were in the blood bank. Now 95. Number decreased.

E) The number of prospective first-time donors is likely to go up by 5 percent. - Do we know anything about first-time donors from the argument? No. Out of scope.

I chose option D because
let x be infected donor and y be total donor. x/3 =y/20(as 55 of actual donor is equal 1/3 of infected donor so from here we get infected donor now constitute 15% of actual donor. Now once the 1/3 of infected donor are qualified the 2/3 of infected donor should be more than 10 % of actual donor as actual donor has decreased.but it remains the same which means the total do or must have remained same. So fulfil the gap the number of 1st time donor must be up by 5% of current actual donor.