Normaaliväestö

Normaaliväestö is a reference or standard population used in statistics, especially in epidemiology and demography, to enable fair comparisons of health indicators between populations with different age structures. It is not a real observed population, but a defined age distribution used for standardization.

The main purpose of using a normaaliväestö is to adjust for differences in age composition so that measures such as incidence or mortality can be compared across populations or over time. Standardization can be performed in two common ways. In direct standardization, the study population’s age-specific rates are applied to the age distribution of the standard population to produce a standardized rate. In indirect standardization, the standard age-specific rates are applied to the study population’s age distribution to yield expected numbers, from which metrics like the standardized mortality ratio or standardized incidence ratio can be derived.

Common choices for a normaali väestö include fixed reference populations such as the World Standard Population or the European Standard Population, or a national standard population chosen for a specific analysis. The exact selection can influence the numerical value of standardized rates, though the goal is to facilitate comparability rather than to reflect the true risk in the standard population.

The concept is used to compare disease burden, mortality, and other health indicators across regions and over time. When presenting standardized results, it is important to specify the chosen standard population so interpretations are clear.