Odds Ratio - Relation To Relative Risk

Relation To Relative Risk

In clinical studies, as well as in some other settings, the parameter of greatest interest is often the relative risk rather than the odds ratio. The relative risk is best estimated using a population sample, but if the rare disease assumption holds, the odds ratio is a good approximation to the relative risk — the odds is p / (1 − p), so when p moves towards zero, 1 − p moves towards 1, meaning that the odds approaches the risk, and the odds ratio approaches the relative risk. When the rare disease assumption does not hold, the odds ratio can overestimate the relative risk.

If the absolute risk in the control group is available, conversion between the two is calculated by:

where:

  • RR = relative risk
  • OR = odds ratio
  • RC = absolute risk in the unexposed group, given as a fraction (for example: fill in 10% risk as 0.1)

Read more about this topic:  Odds Ratio

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