sud21 wrote:What is the accurate rate for a certain disease testing?
1). 96% of the positive results are true, and 90% of the negative results are true.
2). 8% of all people for the testing actually suffered the disease.
Although the stem is missing something in introducing the term 'rate' here, but if we travel around the statements that follow, we can realize that the rate is to be expressed in percent.
We should take there are a total 100 results on testing.
(1) If there are a total 100 results on testing, out of which x are positive with 0.96 x as true, and the remaining 100 - x are negative with 0.90 (100 - x) as true, then the accurate rate for the disease testing is 0.96 x + 0.90 (100 - x) =
90 - 0.06 x. With x unknown, this statement is not sufficient.
(2) If 8% of all people for the testing actually suffered the disease, then 8 is equal to the number of positive results that went true, as per our assumption. Here, we've no idea what is the number of negative results that went true, in order to assess the overall rate of accuracy. With the idea unknown, this statement is not sufficient.
Taking the two statements together, we can have 0.96 x = 8, to find x and calculate the accurate rate for the disease testing as equal to
90 - 0.06 x, really accurately and of course uniquely.
[spoiler]
Sufficient, hence C[/spoiler]
