I was at a talk where mortality rates were presented in one column and the standardized mortality ratio was presented in a different column. I was a bit confused; I could not remember how or why you calculate an SMR. It’s not because SMR calculations are complicated; it’s because my brain can’t remember things as well as it used to. So when I got back to my office, I searched for a web site with a simple tutorial on SMRs with a worked out example. This page popped up right away and I was impressed with the clarity of the writing style.
New Mexico Department of Health. Standardized Mortality Ratio. Available in html format.