Indirect standardization is the procedure of adjusting the crude mortality or morbidity rate for one or more variables by making use of a known reference population. It may, for instance, be needed to compare cancer mortality rates of single and married women with the adjustment being made for the likely different age distributions in two groups. Age-specific mortality rates in the reference population are applied individually to the age distributions of the two groups to obtain the probable number of deaths in each. These can then be summed with the observed number of deaths in the two groups to obtain comparable mortality rates.