In: Statistics and Probability
If an infected person is tested for corona, the probability that the test will give a positive result is 0.60 and if this person is not infected the probability that it will give a positive result is 0.10. Suppose that 2% of the people are corona infected. If one random person is tested for corona using this test, then the probability that the test will give a positive result is
If an infected person is tested for corona, the probability that the test will give positive result, is 0.60.
So,
If a person is not infected , the probability that it will give a positive result is 0.10.
2% of the people are corona infected.
So, the probability that a randomly selected person is corona infected, is 0.02.
So, the probability that a randomly selected person is not corona infected, is 1-0.02, ie. 0.98.
So,
We have to find the probability that the test will give a positive result, for a random person.
Now,
Now, by total probability theorem, this becomes
So, the probability that a random individual tests positive, is 0.11.