Our current capacity to understand or provide a context for interpreting the size of an effect in education program evaluation is limited. To address the problem, this study proposes a time-indexed effect size metric (d') to estimate how long it would take for an "untreated" control group to reach the treatment group outcome in terms…

Through a synthesis of test publisher norms and national longitudinal datasets, this study provides new national norms of academic growth in K-12 reading and math that can be used to reinterpret conventional effect sizes in time units. We propose d' a time-indexed effect size metric to estimate how long it would take for an "untreated"…