The prevalence ratio can also be calculated from the information on CHD and physical activity It is preferable to calculate the prevalence odds ratio when the period for being at risk of developing the outcome extends over a considerable time (months to years) as it does in this example PR = (a/N1) / (c/N0) PR= (50/250) / (50/750) = 30 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 riskHowever, the odds ratio
Odds Ratios The Odd One Out Stats By Slough
