00:02
All right, for this question, we're told that in a population of 10 ,100 people, 100 of the people actually have a disease, and 10 ,000 people are healthy or disease free.
00:13
We're also told that all 100 of the people with the disease will test positive using a test, whereas of the healthy people, 200 will test positive, and 9 ,800 will test negative.
00:24
So first we're asked, what is the probability that the test is correct for someone who has the disease? this is equivalent to saying what is the conditional probability that assuming someone has the disease, that the test comes back positive, meaning it's correct.
00:39
And conditional probability is equal to the probability here of the two events together.
00:49
So in this case, the probability that the test is positive and that the person has the disease divided by the probability that the person has of the disease.
01:02
And we could actually go through and calculate this.
01:06
Actually, yeah, let's do it.
01:07
So we know 100 % of the people who have the disease test positive.
01:11
It's going to be 100 divided by the number of people who have the disease...