Posted by Anonymous on Sunday, September 23, 2007 at 11:20pm.
This is a statistics problem.
A laboratory test for the detection of a certain disease give a positive result 5 percent of the time for people who do not have the disease. The test gives a negative result 0.3 percent of the time for people who have the disease. Large-scale studies have shown that the disease occurs in about 2 percent of the population.
What is the probability that a person selected at random would test positive for this disease?
For this one, I got 0.0194, so 1.94% but I wasn’t sure if the answer is correct.
What is the probability that a person selected at random who test positive for the disease does not have the disease?
This one was confusing to me… I got 0.71637, or 71.637% but I doubt this is right. Please help!
math - drwls, Monday, September 24, 2007 at 9:20am
Consider the four possibilities and their probabilities.
has disease and tests positive:
has disease but tests negative:
has no disease and tests negative:
(0.98)x(0.95) = 0.9310
has no disease but tests positive:
(0.98)x(0.05) = 0.0490
Note the probabilities they add up to 1.000, as they should.
The answer to the first question (positive test probability) is
0.0199 + 0.0490 = 0.0689
The answer to the second question is:
This is a rather large ratio of "false positives" and comes about because the disease is rare (2% of population) and there are many more false positives than "true" positives
math - Anonymous, Monday, September 24, 2007 at 12:09pm
That makes perfect sense. Thank you very much.
math - Anon Ymous, Friday, November 12, 2010 at 8:04pm
hey, we just did this problem in class today...this is from the ap stats 1197 free response prep...the first question's ans. is 0.06894 and the second ques.'s ans. is 0.710763
Answer This Question
More Related Questions
- STAT - The probability of getting a certain disease is 0.2. A certain test is ...
- STAT Help Please! - The probability of getting a certain disease is 0.2. A ...
- probability - Consider a medical screening excersis for a disease that in the ...
- Probability Questions - STAT - 1) The probability of getting a certain disease ...
- statistics - (Blood Test Problem) Suppose 100 people are waiting for blood test...
- probability - A new test for detecting a disease has been developed. Medical ...
- statistics - In a certain population, 1% of all individuals are carriers of a ...
- statistics - A test designed to check for sickle-cell anemia has an 85% chance ...
- Probability - A screening test for a disease shows a positive test result in 95...
- Statistics - A certain disease occurs in 4% of the population. A blood test for ...