In a certain population, the two most heavily diagnosed diseases are s

For this “inference” question, the correct answer must be true based upon the data given in the stimulus. You learn in the stimulus that over the past five years malaria accounted for more than half of all disease cases. IMPORTANTLY, this does not mean that malaria accounted for more than half of all cases each year. You also learn that 5 years ago, schistosomiasis accounted for 40% of all cases but only accounted for 30% over the past year. IMPORTANTLY, you have no idea what percentage schistosomiasis accounted for during the intervening years.

(A) is not necessarily true because you do not know whether the total pie increased. If the pie increased dramatically, then 30% of the bigger number could be larger than 40% of the smaller number.

For (B), no evidence is given about what happened to the percentage data for malaria over the 5 years. All you know is that, in total, malaria accounted for over 50% in that 5 year period.

(C) is likely false, and certainly not guaranteed. If the total number of disease cases went UP, then you would be sure of this. But if the total pie went down by 30%, then all diseases could have experienced a decrease.

For (D), you do not know what the percentages were for each of the intervening years, so you cannot be sure of the statement.

(E) must be true. If the total number of schistosomiasis cases increased, then you know that 30% of last years total disease cases must be greater than 40% of the total disease cases 5 years ago. This guarantees a ratio of 4:3 for this year's disease total to the total 5 years ago, assuring a 33.3% increase. Answer is (E).