Direct versus Indirect Method of Adjustment
Direct method - Assume that the observed population had the same distribution of CHARACTERISTICS as the reference population. Apply the experience of the observed population to the reference population. Direct age adjustment methods apply age specific rates or the experience from study populations to an age distribution from a reference population.
However, when age-specific rates are unavailable in the study populations, we use the indirect method of adjustment.
Indirect method - Assume that the observed population had the EXPERIENCEof the reference population. Apply the experience of the reference population to the observed population. The indirect method uses the age specific rates from a reference population to derive the expected number of cases or deaths in the study populations.