Measures of Association (Measures of Effect)
Odds Ratio (OR)
This is the odds of a person with a disease to have been exposed to a risk factor vs. the odds of a person without the
disease being exposed to that same risk factor. This is used in retrospective studies.
Example. Smoking (exposure) vs. Lung Cancer (outcome)
|
Outcome- Lung Cancer |
No Outcome-No Cancer |
Total |
|
|
Exposure –Smoking |
15 |
45 |
60 |
|
No Exposure- No Smoking |
6 |
24 |
30 |
OR=Odds of someone with cancer having smoked/ Odds of someone without cancer having smoked= (15/45)/(6/24)= (24*15)/(45*6)=1.33
This would be calculated for a case control study (retrospective design).