3. To calculate the association between flea bites and plague, a 2x2 table can b

Question

3. To calculate the association between flea bites and plague, a 2x2 table can be used to categorize people based on disease and exposure status. Let's say there are 100 people in a study, 60 with plague and 40 without. Of those with plague, 50 reported having a flea bite, leaving 10 who did not have a flea bite. Of those who did not have plague, 15 had a flea bite and 25 did not. Using this information, the boxes of the 2x2 table can be filled in as seen below. a)

(5)What study design is this?

calculate the approproate outcome measure or measures

interpret the outcome

plage No plague Total

Flea bites 50 15 65

No flea Bites 10 25 35

Total 60 40

Explanation / Answer

This is a cross sectional study design as disease and exposure status are calculated at the same time. The outcome that is measured here is called the odds ratio, which is the measure of association between an exposure and its outcome. The OR represents the odds that an outcome will occur given a particular exposure, compared to the odds of the outcome occurring in the absence of that exposure.

The OR = (a*d) / (b*c) = (50*25)/(10*15) = 8.33

This means that those with flea bites are 8.33 more likely to have plague, than those without flea bites.

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