Standardization

The objective of standardization is the compare the rates of a disease (or outcome) between population which differ in underlying characteristics (age, sex, race, etc) that may affect the overall rate of disease; In essence it's another way to account for confounding.

Standardization of Rates

The difference between crude rates and standardized rates is that the crude rates are calculated on the population under study, whereas standardized rates are based on particular characteristic(s) as standard.

If the rates are calculated based on the specific characteristic(s), they are called specific rates (eg. age specific mortality rates, or sex specific mortality rates).

CI of Standardized Rate

Variance:

Standardized Rate is a Weighted Average:

Variance for a Standardized Rate:

There are two approaches to Standardization of Rates:

Direct Standardization (Most Common)

w_i are the frequency from "standard" population, r_i are rates from testing population. Very similar to the "weighted average" method from the last chapter.

• Stratum-specific rates (r_i) from population under study
• Strata distribution (w_i) from a "standard" population
• My rates, standard weights

There are many choices for the 'standard' population.

• Internal Standard - one of the groups under study, total population of the study
• External standard - outside, a larger group (ex. US population)

Indirect Standardization

w_i are the frequency from testing population and r_i are rates from "standard" population.