Stabilization reduced the inverse relationship between student group size and score variance for test-based indicators, especially for groups of 10 to 19 students¶

Claim · All claims
Evidence · 1 study · design r2 · q2
Currency · newest study 2024 · not yet checked against its sources · not reviewed by a person · recheck by 2027: tool and model accuracy changes quickly

Subclaims¶

q2 i? For test-based indicators, unstabilized score variance was higher for groups of 10 to 19 and 20 to 29 students than for groups of 30 or more; after stabilization, variance was lower for all group sizes and small-group variance was more comparable to large-group variance. → Rosendahl 2024

Evidence¶

Rosendahl 2024¶

Rosendahl, M., Gill, B., & Starling, J. E. (2024). Stabilizing school performance indicators in New Jersey to reduce the effect of random error (REL 2025–009). U.S. Department of Education, Institute of Education Sciences, National Center for Education Evaluation and Regional Assistance. https://ies.ed.gov/use-work/resource-library/report/descriptive-study/stabilizing-school-performance-indicators-new-jersey-reduce-effect-random-error

q2 · i? · design · r2

Descriptive analysis comparing variance of unstabilized and stabilized z-scores by group-size band (10–19, 20–29, 30+) for five test-based indicators, shown in figure 6. The article interprets the reduced size–variance relationship as improved reliability; no effect size is printed.

"In unstabilized distributions, variance was higher for groups of 10 to 19 students and, to a lesser extent, for groups of 20 to 29 students than for the overall distribution (groups of 30 or more students) (fgure 6). After stabilization, variance was lower for all student group sizes, and variance for small student groups was more comparable to that for larger student groups."

Discussion¶

Related Claims¶

• Non-test-based indicators such as graduation rates are poorly suited to stabilization models assuming normal distributions, which may impose excessive adjustments — related
• Stabilizing test-based indicators produced substantial changes in simulated CSI designations, with larger schools replacing smaller schools — related
• Stabilization reduced overrepresentation of 10-to-19-student groups in the extremes of score distributions for every test-based indicator, with growth indicators becoming underrepresented — related
• Stabilization makes larger adjustments to scores from smaller student groups and to more extreme scores, as expected — related
• Stabilization changed ATSI designations more than CSI designations, with the median lowest-performing subgroup larger under stabilized indicators — related