All five studies analyzed pre/post student writing samples. The writing, with identifying information removed, was independently evaluated at NWP's national scoring conference. Building on a long tradition of writing assessment, the NWP defined a rigorous framework for evaluating student writing, using "anchor papers"—samples exemplifying each level of achievement—along with descriptive commentary.
More than 7,500 writing samples were scored using a rubric adapted from the 6+1 Traits Writing Model (Culham 2003). The four-point scale was extended to six points in order to increase sensitivity, and language was clarified to enhance reliability.
The rubric addressed six specific attributes of writing: ideas, organization, voice, sentence fluency, word choice, and conventions (Bellamy 2005). Each writing sample also received an overall holistic score.