Gersten and Baker (2001) conducted a meta-analysis of 13 intervention studies with
students with learning disabilities to determine the impact writing interventions (e.g., cognitive
strategy instruction for composing) have on these students and to identify instructional
components associated with the best writing outcomes for them. They reported overall weighted
effect sizes ranging from .41 to 1.17 with an aggregate effect size of .81, which represents a large
effect favoring the selected interventions, for varied measures of writing including standardized
writing tests, quality ratings of student papers, and scores on trait and genre structure rubrics. In
their sample of studies, larger effect sizes were associated with true experiments in comparison
with quasi-experimental studies, whereas smaller effect sizes favoring the treatment group were
observed when a control group received some form of writing instruction rather than simply
engaged in writing practice. Contrary to findings reported in most meta-analytic studies, effect