<p>Hi guys,</p>
<p>A certain disease occurs in 1 person out of every 101 person. A test for disease is 100 % accurate for patients with the disease and 99 % accurate for patients without it. That is,it gives a “false positive” 1 % of the time even if the person tested doesn’t have the disease. If you take this test and it returns a positive result,what is the probability that you have the disease?</p>
<p>1)1
2).99
3).95
4).50
5).01</p>
<p>The key to this problem is finding out, of the people who get a positive result, how many have the disease and how many don’t. We know that from a group of 101 people, 1 person will have the disease (and test positive). The remaining 100 people have a 99% chance of testing negative. That means one person will test positive. Therefore, out of the 2 people who test negative, only one will have the disease. The answer is .5.</p>
<p>I see that makes perfect sense thanks alot :).</p>