Question

For a particular disease, the probability of having the disease in a particular population is 0.04. If someone from the population has the disease, the probability that she/he tests positive of this disease is 0.95. If this person does not have the disease, the probability that she/he tests positive is 0.01. What is the probability that a randomly selected person from the population has a positive test result

Answer 1

4.76% probability that a randomly selected person from the population has a positive test result

Explanation:

We have these following probabilities:

4% probability of having the disease.

If a person has a disease, 95% probability of a positive test.

100-4 = 96% probability a person does not have the disease.

If a person does not have the disease, 1% probability of a positive test.

What is the probability that a randomly selected person from the population has a positive test result

95% of 4% and 1% of 96%. So

p = 0.95*0.04 + 0.01*0.96 = 0.0476

4.76% probability that a randomly selected person from the population has a positive test result