odds ratio vs relative risk--#11

what are the difference between odds ratio and relative risk?

**Odds ratio** = disease exposed group/disease unexposed group; r/t case-control studies; **Relative Risk** = disease risk exposed group/disease risk unexposed group; r/t cohort studies; major method for evaluation of risk, but does not explain "why?"

Analyzing 2x2 table data, Odds ratios, relative risk

If you are analyzing risk data where exposed/unexposed is on the x-axis and cases/non-cases are on the Y-axis (such that A=Exposed Cases, B=Unexposed Cases,C=Exposed Non-Cases, and D=Unexposed Non-Cases)

Crude RR=(A*(B+D))/B/(A+C)

Crude Risk Difference=(A/(A+C))-(B/(B+D))

95% Confidence Interval= EXP(LN(Crude RR) [+ or -] 1.96*SQRT((((B+A)*(A+C)*(B+D))/((B+D)+(A+C))^2-A*B/(A+B+C+D)) / ( (A*(B+D)/(A+B+C+D)) * (B*(A+C)/(A+B+C+D)))))

Great FREE calculator for 2x2 study data if you have an iPhone/iPad/iPod Touch - it is an App called "iEpidemiology" You can find it in the Apple App store, I highly recommend it!!