Evaluating Your Hypothesis
After you return from conducting these interviews, you tell Barstow that your working hypothesis is that the epidemic was probably initiated by a single person, most likely a food handler working in the Dairy Queen, or the Sparta Bakery (also known as "Lenny's" Bakery), or Chi Chi's. Now you need to decide how you will go about conducting an analytical study in order to test these hypotheses in order to establish the source of the outbreak. You may find the following article helpful.
The next series of questions deals with potential biases that might affect the results of our analytical study. You may want to review our online module on Bias from the core course.
Analysis and Interpretation
You and Barstow and his staff have collected data from all of the available cases and from a comparison group of non-diseased subjects matched by age and by neighborhood. A portion of the collected data is provided in the accompanying file:
Analyze these data to test the hypothesis that hepatitis was transmitted as the result of exposure from the Dairy Queen, Chi Chi's, or the Sparta (Lenny's) Bakery. You will have to test each of these hypotheses separately.
[Hint: Organize the counts of exposed & unexposed cases & controls into a 2x2 table. The Epi_Tools.XLS Excel spreadsheet may also be useful for computing the confidence intervals for the measures of association that you need to compute. (See Other Resources on the right side of the page.)]
