A pharmaceutical firm has discovered a new diagnostic test for a certain disease that has infected 1% of the population. The firm has announced that 95% of those infected will show a positive test result, while 98% of those not infected will show a negative test result. What proportion of tests results are correct?
my mind is going in circles!
Feb 23rd 2009, 02:26 AM
What we have here is:
* 1% are infected
* 99% are NOT infected
We have to find two probabilities here:
(1) an infected person test shows positive result (correct result): (Let A)
It's 95% of 1% so, P(A) = 0.95 * 0.01 = 0.0095
(2) a person who is not infected shows a negative (correct) result in the test: (Let B)
It's 98% of 99% so, P(B) = 0.98 * 0.99 = 0.9702
So success rate would be P(A) + P(B) = 0.9702 + 0.0095 = 0.9797
Feb 23rd 2009, 02:33 AM
i did not think somone would come to the rescue in time :S