Evidence-appraisal glossary
Standardized mortality ratio
A standardized mortality ratio (SMR) is the number of deaths observed in a study group divided by the number expected if that group had the death rates of a reference population, matched on factors like age and sex. A value of 1 means as many deaths as expected, above 1 means more, and below 1 means fewer.
Also called: SMR.
The SMR comes from indirect standardization and is often multiplied by 100, so an SMR of 120 means 20 percent more deaths than expected. It is a practical way to flag whether a workforce, region, or patient group has unusually high or low mortality once age and sex are accounted for. A key caveat is that SMRs from different study groups are not directly comparable to each other, because each is calculated against the expected deaths generated by its own group's composition rather than a shared standard.
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This is a plain-language methodology definition for reading research. It is general education, not medical advice.