Hepatitis A, Restaurant Example

Several patients were diagnosed with Hepatitis A. The local Restaurant A was thought to be the source of the infection. 40 case patients and a similar disease free group of control were contacted to determine if they ate at Restaurant A.


2 x 2 Table of Data


Odds of exposure in cases = a÷c = 30 ÷ 10 = 3

Odds of exposure in controls = b÷d = 36 ÷ 70 = 0.51

Odds Ratio = Odds of exposure in cases ÷ Odds of exposure in controls = 3 ÷ 0.51 = 5.83

This means that people who ate at Restaruant A were 5.8 times as likely to develop Hepatitis A than were people who did not eat there.

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