What is the probability that a person has the disease given that the test result is positive?
the probability that the test result is positive (suggesting the person has the disease), given that the person does not have the disease, is only 2 percent; the probability that the test result is negative (suggesting the person does not have the disease), given that the person has the disease, is only 1 percent.
What is the probability that an individual tests positive or is disease free?
If a person is free of the disease, then the probability that the diagnostic test comes back positive is 1 − P ( T − | H ) = 0.05 .
What is the probability of a positive test for a disease?
Summary: If a test for a disease is 98% accurate, and you test positive, the probability you actually have the disease is not 98%. In fact, the more rare the disease, the lower the probability that a positive result means you actually have it , despite that 98% accuracy.
What is the conditional probability that you have the disease?
But the conditional probability that you have the disease if you test positive, the positive predictive value, is The number of sick people with positive results is on top of both fractions, but the first fraction has the total sick people on the bottom and the second fraction has the total positive results.
What is the probability of Bob having the disease?
There are 980 + 180 = 1160 people who tested positive in the sample population. Of these people, 180 have the disease. In other words, given that Bob is in the “tested positive” population, his chance of having the disease is 180/1160 = 15.5%.
What is the sum of the probabilities of no disease?
The events, Disease and No Disease, are called complementary events. The “No Disease” group includes all members of the population not in the “Disease” group. The sum of the probabilities of complementary events must equal 1 (i.e., P (Disease) + P (No Disease) = 1). Similarly, P (No Disease | Screen Positive) + P (Disease | Screen Positive) = 1.