Purpose: Many children begin school with limited vocabularies, placing them at a high risk of academic difficulties. The goal of this study was to examine the effects of a vocabulary intervention program, Story Friends, designed to improve vocabulary knowledge of at-risk preschool children. Method: Twenty-four early-childhood classrooms were…

In experimental studies, researchers are often interested in secondary research questions that explore important aspects of main findings, such as whether or not program effects vary according to the level of fidelity in which the program has been implemented; or according to the dosage received by individuals participated in the program. In this…