This tool can be used to calculate a standardized mean difference in vertically scaled scores from pretest to posttest for single-group studies of students in grades 1–12, as measured by common standardized measures (measures and score types are listed below).
For comparison, this tool will display the standardized mean difference for 12 months of typical academic growth (spring to spring) for the same grade level and content area from the assessment’s normative sample at the 10th, 25th, and 50th percentiles. These figures represent the growth required for a student to maintain his or her place in the distribution relative to same-grade peers from the spring of an academic year to the spring of the following year.
For example, if you studied students in first grade and used the Gates-MacGinitie Reading Tests as a measure of reading outcomes, the table would display your sample’s effect size, followed by the effect sizes on the Gates-MacGinitie extended scale scores from spring of kindergarten to spring of first grade for students at the 10th, 25th, and 50th percentiles in the normative sample.
For more information about the calculations and effect sizes used here, please refer to:
Scammacca, N., Fall, A., & Roberts, G. (2015). Benchmarks for expected annual academic growth for students in the bottom quartile of the normative distribution. Journal of Research on Educational Effectiveness, 8, 366-379. PMC4696502
This calculator can be used for the following assessments and scores:
Select your assessment and grade level, using the dropdown menus below. Then, enter your sample’s pretest mean and posttest mean, calculated using the appropriate scores. Finally, click the “Calculate” button.
| Effect Size for Your Sample |
Effect Size for 1 Year of Growth | ||
|---|---|---|---|
| 10th percentile | 25th percentile | 50th percentile | |
