An age-adjusted rate is a weighted average of the age-specific (crude) rates, where the weights are the proportions of persons in the corresponding age groups of a standard population. The potential confounding effect of age is reduced when comparing age-adjusted rates computed using the same standard population. Several sets of standard population data are included in SEER*Stat. These include the 2000 U.S. standard population as well as standard millions for the U.S. population (1940, 1950, 1960, 1970, 1980, 1990, and 2000), the 1991 Canadian population, the European population, and the world population (see 2000 U.S. Standard Population vs. Standard Million for more discussion). The age-adjusted rate for an age group comprised of the ages x through y is calculated using the following formula:

$aarat{e}_{x-y}=\sum _{i=x}^{y}[\left(\frac{coun{t}_{i}}{po{p}_{i}}\right)\times \text{}100,000\times \text{}\left(\frac{stdpo{p}_{i}}{\sum {}_{j=x}^{y}stdpo{p}_{j}}\right)]$

View the steps to calculate an age-adjusted rate.