1997 National Household Survey on Drug Abuse |
where the ratio adjustment R _{I} can be interpreted as
In equation (1), the constant A is simply a scale factor set equal to [U-L]/[ (1-L)(U-1)], beta are the model coefficients, and Xi is a vector of explanatory variables. The explanatory variables considered in the models consisted of the categorical indicator variables for age group and race/ethnicity. The parameters L and U are the predetermined constants that force the estimated Ri to be
The model parameter vector beta in (1) was estimated by solving the generalized raking equations:
Notice from the above raking equations
that the estimated adjustment R_i
forces the 1994-A estimate to equal the
1994-B estimate for any subpopulation represented by an indicator variable
in Xi. Therefore, for example, if an appropriate indicator for the age
group = 12 to 17 year olds was included in Xi, then the model-based estimate
of the R_i's would produce an adjusted prevalence estimate using the 1994-A
sample that exactly equaled the prevalence estimate generated from the
1994-B sample for the 12 to 17 age group.
This page was last updated on December 30, 2008. |