Block 1: Epidemiology
EPI.4-1: THE ODDS RATIO
 

SESSION OBJECTIVE

At the end of this session you should be able to understand the Odds Ratio as a measure of effect and what it estimates. You should also be able to calculate it from data.

LEARNING ACTIVITIES:

Note that the Odds Ratio has no easily usable counterpart as a measure of occurrence.

It is used in a case-control design study where one has to work backwards from a given number of cases and controls to the probability of exposure, rather than directly measure the probability of disease (measure of occurrence).

Remember the definition:

  D+ D-  
E+ a c M1
E- b d M0
  N1 N0 T

The odds of exposure in the diseased (OED+) is given by

Similarly, the odds of exposure in the non-diseased (OED-) is

Hence




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General Introduction to Occupational Health: Occupational Hygiene, Epidemiology & Biostatistics by Prof Jonny Myers is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.5 South Africa License
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