Test discriminating value equals the coefficient of variation of test scores (tan∅ = SD/mean)¶
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Evidence · 1 study · theoreticalr2·q2
Currency · newest study 2021 · not yet checked against its sources · not reviewed by a person · overdue for a recheck since 2024: tool and model accuracy changes quickly
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q2 i? Discriminating value of a test is defined as tan∅, which equals the ratio of SD to mean of test scores, i.e. the coefficient of variation, bounded 0 ≤ DiscT ≤ 1. → Chakrabartty 2021
Evidence¶
Chakrabartty 2021¶
Chakrabartty, S. N. (2021). Assessment of item and test parameters: Cosine similarity approach. International Journal of Psychology and Educational Studies, 8(3), 28-38. https://dx.doi.org/10.52380/ijpes.2021.8.3.190
q2 · i? · theoretical · r2
Empirical application to the 911-candidate, 50-item Selection Test. The computed test discriminating value was 0.168725, leading the article to conclude the "Test had rather poor discriminating value".
"By (1.6) 𝐷𝑖𝑠𝑐𝑇 = 𝑡𝑎𝑛∅= 𝑆𝑋 𝑋̅ = 0.168725⇒ Test had rather poor discriminating value."
Discussion¶
Related Claims¶
- Item discriminating value as coefficient of variation decreases monotonically as number of correct answers increases, giving a negative difficulty–discrimination relationship — related
- Point-biserial item-total correlation is negatively related to test discriminating value and can be expressed via item and test difficulty and discrimination parameters — related
- Test difficulty value defined as ratio of observed to maximum score vector length times cosine of their angle equals test mean divided by number of items — related
Page metadata
| Field | Value |
|---|---|
type |
claim |
id |
test-discriminating-value-cv |
title |
Test discriminating value equals the coefficient of variation of test scores (tan∅ = SD/mean) |
description |
Test discriminating value equals the coefficient of variation of test scores (tan∅ = SD/mean) |
status |
review |
evidence_strength |
moderate |
newest_evidence |
2021 |
recheck_by |
2024 |
generated |
by process:wiki-ingest on 2026-09-25 |
trust |
unverified — no one has confirmed this page's content |
sources |
1 — chakrabartty-2021 |
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