A commonly used effect size used to quantify research findings is a risk ratio, another word for relative risk. The risk ratio compares the risk of a disease or outcome in one group to risk of the same outcome in another different group. Risk ratios are not the same as odds ratios, though both are commonly used in cancer studies. If the risk ratio is 1, the risk is the same in the two groups being compared. For example, if the risk of metastasis is 30% in those taking drug A and 30% in those taking drug B, then 30/30 = 1. A risk ratio greater than one indicates an increased relative risk: 1.33 translates to 33% greater risk. A risk ratio less than one indicates a lower risk: 0.75 translates to a 25% lower risk. If you use risk ratio/relative risk in your reporting, try to include absolute risk as well.
