**I**n a Limited-Duration Prevalence Session, the Statistic box displayed on the Statistic tab allows you to choose one of the three statistics described below. The statistic you select will not be the only statistic included in the Limited-Duration Prevalence results matrix. Additional statistics in the results matrix will include statistics directly or indirectly used in the calculation of the selected statistic.

Crude Percent is the percent of prevalent cases for the associated population on the prevalence date. When calculating crude percents, the results matrix will include the number of prevalent cases and populations used to calculate the percents. Note that in some cases the populations are the average of populations for two years. For example, if you use a database provided by SEER, the population estimates are mid-year population estimates. Therefore, if you are calculating prevalence on January 1st of a given year then that year's and the prior year's populations are averaged to estimate the January 1st populations.

Age-Adjusted Percent is a weighted average of the crude percents, 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 percents computed using the same standard population. When calculating age-adjusted percents, the results matrix will include the associated counts and populations. Note that in some cases the populations are the average of populations for two years. For example, if you use a database provided by SEER, the population estimates are mid-year population estimates. Therefore, if you are calculating prevalence on January 1st of a given year then that year's and the prior year's populations are averaged to estimate the January 1st populations.

Counts Only is the option to calculate the number of prevalent cases, and not crude or age-adjusted percents.