Use standardization to compare populations with different age compositions after aligning age-specific rates and standard weights exactly.

Age rates

Age-specific rates in the study population, in any consistent unit per person-year.

Standard weights

Reference standard weights or counts for the same age groups.

SDR

Directly standardized rate in the units of the supplied rates.

Weight total

Sum of the standard weights used.

The standardized result is a weighted summary, not an observed crude rate. It changes with the reference population, and incompatible age bands or rate denominators invalidate the comparison.

Report crude and age-specific rates alongside the standardized value, and repeat the calculation with another accepted standard population when comparisons could depend on the chosen weights.

• Age Standardized Prevalence Weighted

  Compute the age-standardized prevalence as the standard-weight weighted average of age-specific prevalences, sum(w_i * p_i) / sum(w_i).

• Indirect Standardized SMR

  Apply indirect standardization: compute expected deaths from standard age-specific rates and study exposure, divide observed by expected deaths for the SMR, and multiply that ratio by the standard population's crude rate to obtain an indirectly standardized rate.

• Kitagawa Component Decomposition

  Split the difference between two crude rates into an age-composition effect and a rate effect using Kitagawa's two-component decomposition with averaged compositions and rates.