00:01
In this column, we first want to know if someone test positive, what's the chance they actually have it? and so the way we can do that is first write out the probability of someone having the disease and then testing positive.
00:17
So the chance that they have the disease is 4%.
00:22
And the chance that they would test positive given that they have the disease is 97%.
00:28
And now in the denominator, we want to write out all the possible way someone could test positive.
00:36
Where the first way is what we just mentioned, that having the disease and testing positive.
00:42
We could also have someone who doesn't have the disease, which has 96 % chance of happening, to test positive anyways, a false positive.
00:52
And that happens 2 % of the time.
00:55
And so if we multiply this out, we get 0 .6690.
01:03
So this means 66 .9 % of the time if someone test positive, they actually have the disease.
01:12
Now for part b, we want to know a patient testing positive for aryan influenza with the test is not infected.
01:20
And so this is very similar to our last problem.
01:22
It's just the last problem tells us the probability that if they test positive, they have the disease.
01:30
Now i want to know the probability that they don't have the disease, whereas just one minus the probability we found last time...