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| Block 1: Epidemiology |
| EPI3-3: RELATIVE MEASURES OF COMPARISON OF DISEASE OCCURRENCE OR MEASURES OF EFFECT |
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| Block 1: Epidemiology |
| EPI3-3: RELATIVE MEASURES OF COMPARISON OF DISEASE OCCURRENCE OR MEASURES OF EFFECT |
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In contrast to absolute comparisons, relative comparisons are based on the ratio of the occurrence of disease in the exposed to the occurrence of disease in the unexposed group.
In Example 1 on the previous page, the incidence proportion ratio of lung cancer between smokers and non-smokers is 0.0010/0.0001 = 10. The numerical value will be quite different for the two types of comparative measures. The fact that the absolute measure of effect (incidence proportion difference) for this example is 0.0009 while the ratio measure is 10 illustrates the contrast between the numerical values.
In the second example the incidence proportion difference is 0.1813 - 0.0952 = 0.0862, while the incidence proportion ratio is 0.1813/0.0952 = 1.90.
For the 3 measures of occurrence, there are also 3 corresponding relative measures of effect:
There is also a 4th measure of relative effect and this is the Odds Ratio. This relates the odds of exposure for the diseased in to the odds of exposure for the non-diseased. The odds ratio is dealt with in a dedicated session later on in this course.
