The problem you must solve is:
Consider a common disorder, which we will call Z, that affects 19% of adults (18 years and over) in the U.S. Fortunately, there is a genetic screening test for the gene that causes disorder Z. 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 Johnsonville, the adult population is 50,000 and all the residents get tested for the gene linked to disorder Z.
- How many of the residents of Johnsonville 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 test resultsactually have the disease?
5.
Compare your results with the problem you solved in the discussion activity (M8D1).
Specifically, focus on the percent of people who get a positive result that actually have
the disease. Remember that both genetic tests were 98% accurate. Why were the
percentages so different? Do you think the rarity of the disease affects testing results?
Why or why not? Be sure to explain your reasoning mathematically.
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