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.
Description
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.
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.1
When to use Indirect Standardized SMR
Use standardization to compare populations with different age compositions after aligning age-specific rates and standard weights exactly.
- Standard rates
- Reference (standard) population age-specific rates in events per person-year.
- Study population
- Study population exposed by the same age groups.
- Observed deaths
- Total deaths observed in the study population over the period.
- Standard crude rate
- Crude event rate in the standard population, expressed in the same units as the age-specific rates.
How the method works
- Expected
- Expected deaths from applying standard rates to study exposure.
- SMR
- Standardized mortality ratio, observed divided by expected deaths.
- Crude rate
- Crude death rate of the study population per person-year.
- Standardized rate
- Indirectly standardized rate: the standard population's crude rate multiplied by the SMR.
Limitations and assumptions
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.
Alternative or Complementary measures
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.
References
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Age adjustment — Wikipedia contributors
Similar or alternative tools
- 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).
- Direct Standardized Rate SDR
Compute the directly age-standardized rate as the standard-population-weighted average of age-specific rates, SDR = sum(m_i * W_i) / sum(W_i).
- 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.