thelosthippie wrote:
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.
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)
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