This paper was intended to promote a deeper understanding of a statistical method called balancing developed by National Assessment of Educational Progress. Problems in estimating main effects when populations are disproportionate, balancing solutions to these problems, methods equivalent to balancing, interpretation of balanced results, and some applications are considered and accompanied with examples. It is concluded that properly balanced results or the adjusted marginal means should be considered in studies in which group status or group comparisons are of a major concern. The process of balancing can be used to identify variables relating to outcome measures, and to test for spuriousness of the group effects. (Author) Aspect of National Assessment (NAEP) dealt with in this document: Procedures (Analysis).