hesela.devDirect standardization
Direct standardization compares populations by applying the same reference weights to their stratum-specific rates.
The reference weights are nonnegative and sum to one; the same strata and weights must be used for each comparison. NCHS describes this approach for age-adjusted population rates. A standardized rate is a comparison summary rather than the study population's crude rate. [1]
For exposure-based storage rates, Hesela uses a declared reference drive-time distribution and rates in failures per 100 drive-years. The synthetic example gives 4% and 3% under equal age-band weights, while the observed aggregates of the invented inputs are 2.4% and 4.6%. No human population standard is applied to disks, and these are not failure probabilities. [2]
Missing or zero exposure does not provide a zero rate. State the target population, age-band definitions, coverage and sparse strata. Common weights do not by themselves control other differences or turn an observational comparison into a causal estimate. [2]