I thought this example Lisa Martinez made in the comments at the Well blog was one of the clearer examples I’ve seen for absolute vs relative risks.
100 women took ABC pill and 100 women took a placebo, which is not an actual medication. Of the 100 women who took ABC pill, 2 developed cancer and of the 100 women in the placebo group, 4 got cancer. It is reported that this clinical trial showed a 50% reduction in cancer and another report states that the same clinical trial showed a 2% decrease in cancer. Both percentages are accurate and that is because the data are being reported in two different ways.
The 50% reduction was reported using relative risk reduction. The 2% decrease was reported using absolute risk reduction. It is extremely important that you understand the difference between the two when making decisions about your care. So when presented with options for chemotherapy or any treatment, make sure you ask your healthcare provider to give you the relative and the absolute risk reduction percentages.
Many publicists and news articles on the risks of weight use relative risks not absolute. As you can see, this can be a BIG difference!