Alpha of knowledge tests is substantially related to the number of items in the test¶
Claim · All claims
Evidence · 1 study · quant-synthesisr2·q3
Currency · newest study 2025 · not yet checked against its sources · not reviewed by a person · recheck by 2028: tool and model accuracy changes quickly
Subclaims¶
Reading the evidence codes
q is the design tier, i the impact, n the sample, and the kind with its r
the rigour judged within that kind: what each code means.
This claim: no standardized effect is recorded in observations/ for it yet, so no benchmark reading is possible.
q3 i? There is a substantial positive relation between the number of items and Alpha, appearing less quadratic than hypothesized. → Peter A. Edelsbrunner 2025
Evidence¶
Peter A. Edelsbrunner 2025¶
Peter A. Edelsbrunner, Bianca A. Simonsmeier, Michael Schneider. (2025). The Cronbach’s Alpha of Domain‑Specific Knowledge Tests Before and After Learning: A Meta‑Analysis of Published Studies. Educational Psychology Review. https://doi.org/10.1007/s10648-024-09982-y
q3 · i? · quant-synthesis · r2
Meta-analytic regression with log-transformed number of items (range 3–150, median 20) showed a substantial association with Alpha (p < .001, Table 2). The relation appeared "less quadratic than we had expected" based on the Alpha formula.
"there was a substantial relation between the number of items and Alpha, potentially with a moderate exponential or quadratic tail in the lower end of the distribution"
Discussion¶
Related Claims¶
- Alpha is negatively related to sample mean age, and knowledge type shows no effect after controlling for test length — related
- Published knowledge test Alphas show distributional bias with underrepresentation of low Alphas — related
- Open response format is associated with higher Alpha than multiple choice in knowledge tests — related
- Meta-analytic average Cronbach's Alpha of domain-specific knowledge tests is 0.85 with expected item intercorrelation of 0.22 — related
- Cronbach's Alphas of knowledge tests vary widely, with a 90% prediction interval of (0.35, 0.96) — related
- Adding items to a knowledge test can increase reliability without requiring the added items to be redundant with existing items — a broader claim this one bears on
Page metadata
| Field | Value |
|---|---|
type |
claim |
id |
knowledge-test-alpha-test-length |
title |
Alpha of knowledge tests is substantially related to the number of items in the test |
description |
Alpha of knowledge tests is substantially related to the number of items in the test |
status |
review |
evidence_strength |
moderate |
newest_evidence |
2025 |
recheck_by |
2028 |
generated |
by process:wiki-ingest on 2026-10-19 |
trust |
unverified — no one has confirmed this page's content |
sources |
1 — peter-a-edelsbrunner-2025 |
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