Epidemiologist: In Brazil, schistosomiasis and malaria are the two mos

Question

Epidemiologist: In Brazil, schistosomiasis and malaria are the two most common infectious diseases. Over the past five years, schistosomiasis has been primarily responsible for the overall increase in infectious disease cases. Therefore it is likely that there were more cases of schistosomiasis than malaria five years ago.

Which of the following most strengthens the argument above?

A. Over the past five years, the percentage of infectious disease cases caused by schistosomiasis has remained unchanged, but the percentage of cases caused by malaria has increased substantially.
 
B. Trends in infectious disease data tend to persist for decades, unless there is a major breakthrough in treatment regimens.
 
C. Five years ago, many more people died from schistosomiasis than died from malaria. 
 
D. Over the past five years, the percentage of infectious disease cases caused by malaria was not significantly greater than the percentage of cases caused by schistosomiasis.
 
E. Over the past five years, the percentage of infectious disease cases caused by diseases other than malaria and schistosomiasis did not increase substantially.

KarishmaB · Accepted Answer

Yes, the argument is analytical. Let's understand it first.

Two most common infectious diseases: schistosomiasis and malaria
Infectious disease cases have increased in the past 5 yrs (say from a total of 100 five yrs ago to 150 now). Schistosomiasis led to this increase so probably many of the extra 50 cases are those of Schistosomiasis.
Conclusion: It is likely that there were more cases of schistosomiasis than malaria five years ago i.e. say 5 yrs ago, there were 70 schistosomiasis cases while there were 20 malaria cases (and 10 other disease cases)

We need to strengthen the conclusion.

A. Over the past five years, the percentage of infectious disease cases caused by schistosomiasis has remained unchanged, but the percentage of cases caused by malaria has increased substantially.
If most of the increase in cases is due to schistosomiasis but the % of schistosomiasis in the total cases is the same, it means, most of the cases comprised of schistosomiasis earlier too. So this strengthens our conclusion. Let's take a look using numbers too.

Today if still 70% infectious disease cases are those of schistosomiasis, it means there are 105 schistosomiasis cases today (an increase of 35 out of the extra 50). 
If malaria cases have increased to 30%, number of malaria cases would be 45 i.e. an increase of 15 out of the extra 50. 
We see that schistosomiasis cases account for most of the extra 50 cases i.e. they account for 35 cases. So this strengthens our conclusion.
 
B. Trends in infectious disease data tend to persist for decades, unless there is a major breakthrough in treatment regimens.
We don't know if there has been a major breakthrough in treatment regimens on any disease in the past 5 yrs. It is possible that 5 yrs ago there were more cases of malaria than schistosomiasis but breakthrough in treatment regimen of malaria led to a decline in its cases. 
 
C. Five years ago, many more people died from schistosomiasis than died from malaria. 
Number of deaths is irrelevant to the number of cases since the argument doesn't say which disease is more serious, has better medicines etc. It is possible that schistosomiasis had fewer cases 5 yrs ago but is much more serious and led to death more often. 
 
D. Over the past five years, the percentage of infectious disease cases caused by malaria was not significantly greater than the percentage of cases caused by schistosomiasis.
This says that % of malaria cases was not much greater (though perhaps a little greater) than % of schistosomiasis cases over the past 5 years. If anything, this weakens our conclusion. It indirectly implies that out of 100 cases 5 yrs ago, malaria cases were slightly more than schistosomiasis cases. 
 
E. Over the past five years, the percentage of infectious disease cases caused by diseases other than malaria and schistosomiasis did not increase substantially.
This says that % of other diseases has held steady. So if earlier, 10% of cases (10 cases) were other diseases, still 10% of cases (i.e. 15 cases) are other diseases. This doesn't say whether 5 yrs ago there were more cases of schistosomiasis or malaria.

Answer (A)

ssbisht · Answer

Fact1: In Brazil, schistosomiasis and malaria are the two most common infectious diseases.

Fact2: Over the past five years, schistosomiasis has been primarily responsible for the overall increase in infectious disease cases.

Conclusion: it is likely that there were more cases of schistosomiasis than malaria five years ago.

choice A is the correct answer because:

fact2 says that schistosomiasis has been primarily responsible for the overall increase in infectious disease cases over past 5 years.

Now if its percentage has remained unchanged as said in choice A then that means that it was already having more cases as even with same percentage it is still primarily responsible for the overall increase in infectious disease cases as compared to malaria whose percentage has increased.

chetan2u · Answer

Epidemiologist: In Brazil, schistosomiasis and malaria are the two most common infectious diseases. Over the past five years, schistosomiasis has been primarily responsible for the overall increase in infectious disease cases. Therefore it is likely that there were more cases of schistosomiasis than malaria five years ago.

Which of the following most strengthens the argument above?

A. Over the past five years, the percentage of infectious disease cases caused by schistosomiasis has remained unchanged, but the percentage of cases caused by malaria has increased substantially.
 CORRECT...lets look at the logic. even though the % of infectious disease cases caused by schistosomiasis(S) has remained unchanged and the percentage of cases caused by malaria(M) has increased substantially, still schistosomiasis(S) has been primarily responsible for the overall increase in infectious disease cases.....
 ]this can be only possible if the number of schistosomiasis are way more than malaria five years ago, as a small %increase of a large S will result in a greater number than a high % in a smaller M

B. Trends in infectious disease data tend to persist for decades, unless there is a major breakthrough in treatment regimens.
 Out of scope- major breakthrough in treatment

C. Five years ago, many more people died from schistosomiasis than died from malaria. 
 the number of deaths may not necessarily give you more number of cases of that diseases....
It is possible that the cases of schistosomiasis were less but so severe that many of them were fatal.

D. Over the past five years, the percentage of infectious disease cases caused by malaria was not significantly greater than the percentage of cases caused by schistosomiasis.
doesn help much

E. Over the past five years, the percentage of infectious disease cases caused by diseases other than malaria and schistosomiasis did not increase substantially.
 out of scope 
A

aditya111 · Answer

Can someone quite eloborate on answer choices , i'm not quite getting this. please.

I feel C is the correct answer . Question analysis: schistosomiasis ->major cause in overall increase in infectious disease cases conclusion: there were more cases of schistosomiasis thanb of malaria five years ago. So we know that the percentage growth of schistosomiasis is greater to the percentage increase of malaria over the five years . If only we can prove malaria and schistosomiasis were of same levels before five years or schistosomiasis was of much higher level than the cases of malaria we wold have achieved our goal. Only option C satisfies this. Please confirm the answer choice someone. Very good question.

ssbisht · Answer

Hi,

Please look at my comments inline:
 
Question analysis:

schistosomiasis ->major cause in overall increase in infectious disease cases :  You are correct here

conclusion: there were more cases of schistosomiasis thanb of malaria five years ago.

So we know that the percentage growth of schistosomiasis is greater to the percentage increase of malaria over the five years : Wrong we cant assume this. 
May be the base of malaria was so small that a greater percentage will not mean more cases.Ex lets assume 10 cases of malaria and 90 of schistosomiasis means even if malaria grows my 100% to 20 and schistosomiasis doesnt grow,still schistosomiasis will contribute more cases.

If only we can prove malaria and schistosomiasis were of same levels before five years or schistosomiasis was of much higher level than the cases of malaria we wold have achieved our goal.
 You are right here and this is proved by option A. .
The reasoning is that as per option A ,the percentage of infectious disease cases caused by schistosomiasis has remained unchanged, but the percentage of cases caused by malaria has increased substantially and  yet schistosomiasis has been primarily responsible for the overall increase in infectious disease cases. .This means that schistosomiasis was of much higher level than the cases of malaria9as you have said above).

Only option C satisfies this.  Wrong as option C talks only about death and not about number of cases  so easy to eliminiate this option.

In these kind of question try to eliminate as many option as poosible so that your foucus is on understanding the implication of the options remaining.
Hope this helps.

gmatprav · Answer

A seems the best for the following reasoning, though I went with A, D seems very close, any alternate explanation why D can be eliminated?
 
A. Over the past five years, the percentage of infectious disease cases caused by schistosomiasis has remained unchanged, but the percentage of cases caused by malaria has increased substantially.
 From the argument, we gather that Schist  has been  primarily responsible for overall iincrease in ifectious diseases. Now lets come to this answer. Schist percentage remains same. With this infor schist is still major contributor, so let us safely assume that schist makes up 60% of infectious diseases. If malaria made significant increases, then malaria may have gone from 15% five years ago to 40% now, still a substantial increase. Therefore this answer gives us good reason to believe schist had more cases than malaria five years ago  Correct answer.
B. Trends in infectious disease data tend to persist for decades, unless there is a major breakthrough in treatment regimens.
  The words like  tend to  imply a good possibility, but this in itself is not sufficient to best support above argument. 
C. Five years ago, many more people died from schistosomiasis than died from malaria. 
  This choice is misleading, more deaths does not mean more cases of infection. 
D. Over the past five years, the percentage of infectious disease cases caused by malaria was not significantly greater than the percentage of cases caused by schistosomiasis.
  This only talks about past 5 years, this choice does not rule out possibility of more cases of malaria 5 years ago 
E. Over the past five years, the percentage of infectious disease cases caused by diseases other than malaria and schistosomiasis did not increase substantially.
 Other diseases not increasing does not give us enough information to make a comparison between Malaria and schist.

Kellykailin · Answer

Here are the mathematical proof that answer 1 is correct.

Posted from my mobile device

srishti201996 · Answer

mikemcgarry   GMATNinja   VeritasPrepKarishma

Can you please shed more light on D?

Karishma you gave the following explanation :

D. Over the past five years, the percentage of infectious disease cases caused by malaria was not significantly greater than the percentage of cases caused by schistosomiasis.
This says that % of malaria cases was not much greater (though perhaps a little greater) than % of schistosomiasis cases over the past 5 years. If anything, this weakens our conclusion. It indirectly implies that out of 100 cases 5 yrs ago, malaria cases were slightly more than schistosomiasis cases.

Can you please tell me if my understanding of this is correct?
Say there were 100 cases 5 years ago!
51%-M - 51 cases
49%-S- 49 cases

so S cases were less than M but since now S is the cause of most cases, S would have increased over time.

But we can't say S was greater 5 years ago?

Am i right?

HG0815 · Answer

Very tough..IMO OA is A
In my case, I was confused between A and E
This is my reasoning

A. Over the past five years, the percentage of infectious disease cases caused by schistosomiasis has remained unchanged, but the percentage of cases caused by malaria has increased substantially.
 -> Keep
B. Trends in infectious disease data tend to persist for decades, unless there is a major breakthrough in treatment regimens.
 -> 'treatment regimens' : Out of scope
C. Five years ago, many more people died from schistosomiasis than died from malaria. 
 -> incorrect. 
 Let's suppose malaria is more fatal than schistomiasis. Then we do not need to think about the percentage. 
D. Over the past five years, the percentage of infectious disease cases caused by malaria was not significantly greater than the percentage of cases caused by schistosomiasis.
 -> Incorrect. This is just a fact.
E. Over the past five years, the percentage of infectious disease cases caused by diseases other than malaria and schistosomiasis did not increase substantially.
 -> Keep

I chose A, because let's suppose there is another disease C. 
If the percentage of C is 90%, then E can weaken the passage.
But in A, for example, the percentage of schistosomiasis was always 50%, but the percentage of malaria was changed suddenly
,for example, 5% to 50%(Because schistosomiasis was always 50%), it can strengthen the passage.

KarishmaB · Answer

C cannot be 90% since two most common infectious diseases are malaria and schistosomiasis.

(E) is irrelevant since we are comparing malaria vs schistosomiasis increase. What happened to the number of others is immaterial.

We see that number of schistosomiasis cases has increased substantially. If the percentage of infectious disease cases caused by schistosomiasis has remained same, but the percentage of cases caused by malaria has increased substantially but still in actual number terms, the number of cases of schistosomiasis is the same, it could mean that the initial percentage of schistosomiasis cases was more.

Say if x% cases were of schistosomiasis 5 yrs ago and y% of malaria, assuming that the percentage of cases of schistosomiasis remains constant, when will they account for most of the new disease cases? The number of new cases of schistosomiasis will be x% of the additional number of total cases. They will be majority of the new cases if x > 50%. 
Hence (A) works.

KarishmaB · Answer

If schistosomiasis has been primarily responsible for the overall increase in infectious disease cases over the past 5 years and we want to conclude that there must have been more cases of schistosomiasis 5 years ago, we need to say that percentage of schistosomiasis cases has either remained same or decreased slightly. 
Only then , if today too they are majority in number in the extra cases, they must have been majority in number 5 years back too.
So (A) works.

Let's look at (D).
Over the past five years, the percentage of infectious disease cases caused by malaria was not significantly greater than the percentage of cases caused by schistosomiasis.
(D) says that percentage of malaria cases was not significantly greater than percentage of schistosomiasis cases. We actually want the percentage of schistosomiasis cases to be higher than those of malaria over the past 5 yrs so that majority of extra cases are of schistosomiasis. So option (D) does not work.

mikemcgarry · Answer

Dear srishti201996 , I'm happy to respond.

My friend, context is everything. The prompt says, " Over the past five years, schistosomiasis has been primarily responsible for the overall increase in infectious disease cases ." That's evidence. That means that when we look at the total number of new cases of infectious disease, schistosomiasis accounts for well over 50% of them. If the number new cases of malaria were anything close, anything comparable, to the number of new cases of schistosomiasis, then this statement would be false. To say one thing is primarily responsible is to say that all other things combined are, in aggregate, not as powerful, not as influential, as that one thing. This is absolutely crucial to keep in mind with this argument. Choice (D) directly contradicts this piece of evidence. D. Over the past five years, the percentage of infectious disease cases caused by malaria was not significantly greater than the percentage of cases caused by schistosomiasis. If about the same number of people had one or the other, then it would be patently false to say that only schistosomiasis was " primarily responsible for the overall increase in infectious disease cases ." This directly contradicts the evidence in the prompt. That's not the sign of a good strengthener! Does this make sense? Mike

AdityaHongunti · Answer

Epidemiologist: In Brazil, schistosomiasis and malaria are the two most common infectious diseases. Over the past five years, schistosomiasis has been primarily responsible for the overall increase in infectious disease cases. Therefore it is likely that there were more cases of schistosomiasis than malaria five years ago. 
Understand :
1) S and M are most common   S and M account for more than 50 (S+M>50%) 
2 )S is the major contributor for the   INCREASE   for IDs

Conclusion: FIVE YEARS AGO - number of cases of S>M ( note : NUMBER OF CASES)

Prethinking :
let cases with scisht = S
Cases with malaria = M
other cases = O
Therefore : S+M+O =100

New cases =50
S= 30 (assumed as per given info as S is MAJOR contributor for INCREASE)
M= 15( assumed as per given info as S and M both are MOST COMMON so M will still be GREATER than OTHER cases
O=5

Conclusion : before the increase S>M

Do not try to prethink here as there will be 3 cases which you would have to test in order to concur with the conclusion

ANswer choices :

A. Over the past five years, the percentage of infectious disease cases caused by schistosomiasis has remained unchanged, but the percentage of cases caused by malaria has increased substantially.
: Now as per given ans choice the percentage of cases 5 years ago and over past 5 years is the SAME and percentage of M has inreased (Note: percentage is given and not numbers)
5 years ago : no. of Schiest = S
suppose S account for (x) percent for all cases.--- S= (x)/100 * total cases (100) ........ (1)

over past 5 yrs : total number of sciest cases : S+30
As per A : S+30 = (x)/100 * new total cases (150)........ (2)

Therefore : substitute value of  (x)/100  from (1) in (2)

S+30= S/100 *150
Solve for S >> S=60

Therefore , M has to be less than or equal to 40 but cannot be greater than 40..... Therfore the conclusion = S>M

dcummins · Answer

Official Veritas  Explanation

The logic in the original argument is clearly flawed. You are given two premises: 1. The total number of infectious disease cases is growing (in other words the size of the pie has increased), and 2. Of those new cases, schistosomiasis accounts for the greatest number. Then the conclusion erroneously states that there were likely more cases of schistosomiasis than malaria 5 years ago. There is a huge gap between the two premises and the conclusion. What if, if for instance, there were 5000 cases of malaria 5 years ago and 1,000 cases of schistosomiasis. In the past 5 years, there could have been 500 new cases of schistosomiasis and only 100 new cases of malaria.

Then you have met all the conditions given by the premises (the total has increased and schistosomiasis has accounted for a majority of those cases) but there were clearly more malaria cases than schistosomiasis cases 5 years ago. You need something that removes this possibility and increases the likelihood that there were more cases of schistosomiasis than malaria 5 years ago. Answer choice (A) does this perfectly (it guarantees the conclusion), but it is very difficult to comprehend because of the difficult presentation of data.

Combining (A) with the premises in the original stimulus, you know that schistosomiasis accounted for the most number of new cases over the past five years AND its percentage of the pie remained unchanged. Malaria accounted for fewer new cases AND its percentage of the pie INCREASED. This means that there must have been more cases of schistosomiasis 5 years ago than malaria cases. If there had been more malaria cases, then an increase in its percentage of an increasing pie would have meant that it accounted for more new cases than schistosomiasis. (B) and (C) are relatively easy to eliminate because the death rates are not relevant and the trends may or may not have changed over the time period as you know nothing about what has happened with treatment regimens. (D) is the difficult sucker choice and is the opposite of answer choice. You need the percentage of new cases to be higher for malaria in order to prove this conclusion, so (D) is wrong. In (E) the percentage of other infectious diseases is not important, as it does not affect the important relationships between malaria and schistosomiasis in this conclusion. Answer is (A).

ssharitija · Answer

Hello Chetan,

The explanation for statement (A) seems so logical to me. However, I have a doubt. Is the question not referring to percent over the last five years (= Number of cases of disease caused by schistosomiasis /Total number of cases of Disease)? How can we calculate the percent during last five years as a fraction of number of cases before 5 years?

Saasingh · Answer

I found a very novel approach for this question which I would like to share ----> growth graph.

Do plot the graph as you read solution to understand better.

For answer A:

Place imaginary points for "todays" scenario. S>M. Also S is primarily responsible for total increase.
Plot points Total, S, M on graph. For example to visualize: put Total= (5,5), S = (5,4) and M = (5,2).

Now, option A says, % of S/T is same today as 5 years ago.
Plot points for this statement. But here is the catch. S/T is same. So, gap between S and T on graph must remain same (in our example Y = 1 is the gap).

Plot points for statement A : put Total= (3,2), S = (3,1). Now what can M be? Statement A: cases of malaria increased significantly. Which means, gap today between M and T(y=2 from graph) is much much less today than 5 years ago. Plot these figures, and see for yourself. So 5 years ago gap between M and Total MUST be alot more than 2. Let it be 5.
So M would be (3,-6). Definitely it strengthens that S >> M which is our conclusion.

Kudos if it helps

Regards

VerbalBot · Answer

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