The standardized mortality ratio (SMR) is the number of observed deaths in a study population divided by the expected deaths in the study population and multiplied by 100. The expected deaths are the number of deaths that would occur if the study population experienced the same age-specific, sex-specific (and sometimes ethnicity-specific) mortality as the reference population. Thus, if the SMR is less than 100, the mortality experience of the study population is less than that of the reference population. The statistic enables easy calculation of the 'excess mortality' which is due to variables other than age, sex or race. Cf. Crude Death Rate.
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