Unavoidable sample size issues beset psychological research that involves scarce populations or costly laboratory procedures. When incorporating longitudinal designs these samples are further reduced by traditional modeling techniques, which perform listwise deletion for any instance of missing data. Moreover, these techniques are limited in their…

Proactive preliminary minimum sample size determination can be useful for the early planning stages of a latent variable modeling study to set a realistic scope, long before the model and population are finalized. This study examined existing methods and proposed a new method for proactive preliminary minimum sample size determination.

In an effort to identify instructional methods that might improve mathematics learning at the grade 4 level when used in a variety of educational settings under typical conditions, the REL Mid-Atlantic research team looked for promising, replicable practices that were being used broadly by teachers in U.S. schools, for which research showed…