Consider a particular genetic disease affects 3% of adults in the U.S. population. Fortunately, there is a genetic test for the gene that causes the disease. The test is 98% accurate; that is, 98% of the people who take the test get the correct result (and 2% of people tested get the wrong result).
In Springfield, there are 100,000 adults, and they all get tested for the disease.
- How many of the residents of Springfield are likely to have the disease?
- How many of the people who actually have the disease get a positive test result?
- How many of the people who do not have the disease get a positive test result?
- Of the people who get a positive test result, how many of them have the disease? Convert this to a percentage: What percent of people who get a positive result actually have the disease?
- What does this percentage tell you about the test?