Where is the mean in the total sample and is the mean in the sub-group, and are their respective effective sample sizes, and is the proportion of the total population in sub-group :
- is the Standard Error of ,
- is 1 if Bessel's correction is selected for Proportions in Statistical Assumptions and 0 otherwise,
- and are the estimated standard deviations for the total sample and sub-groups respectively,
- and are the estimated standard error of the means for the total sample and sub-groups respectively,
- is Extra Deff, and
- is the proportion of the Population represents by the sub-group.