Problem Write-Up

As in the Module 8 Discussion (M8D1), we will consider the town of Springfield, where there are 100,000 adults. Consider a different genetic disease, which affects only 0.1% of the U.S. population. The test for this disease is also 98% accurate. All the adults in Springfield were also tested for this disease.

Use a table to organize your results, like those in the text (e.g., Table 3.7 on page 175) or like one you or a fellow discussion group member may have employed in the discussion. Include this table in your write-up. While referring to this table, answer the following questions:
 

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?

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? State a conclusion about how the rarity of a disease affects testing results.