Educational researchers commonly use the rule of thumb of "design effect smaller than 2" as the justification of not accounting for the multilevel or clustered structure in their data. The rule, however, has not yet been systematically studied in previous research. In the present study, we generated data from three different models…

Equating functions are supposed to be population invariant, meaning that the choice of subpopulation used to compute the equating function should not matter. The extent to which equating functions are population invariant is typically assessed in terms of practical difference criteria that do not account for equating functions' sampling…

The 168 items selected for administration to 7,905 17-year olds in 1976-77, were developed from existing National Assessment items and from existing sets of life/coping skills. Skills designated as basic included: career development; citizenship; community resource utilization; consumer protection; family management; health maintenance; and…