Rating Scale Instrument Quality Criteria

Rating Scale Instrument Quality Criteria
CriterionPoorFairGoodVery GoodExcellent
Targeting *> 2 errors1-2 errors< 1 error< .5 error< .25 error
Item Model Fit Mean-Square Range Extremes< .33 - >3.0.34 - 2.9.5 - 2.0.71 - 1.4 .77 - 1.3
Person and Item Measurement Reliability<.67.67-.80.81-.90.91-.94>.94
Person and Item Strata Separated2 or less2-33-44-5>5
Ceiling effect: % maximum extreme scores>5%2-5%1-2%.5-1%<.5%
Floor effect: % minimum extreme scores>5%2-5%1-2%.5-1%<.5%
Variance in data explained by measures**??????????
Unexplained variance in contrasts 1-5 of PCA of residuals>15%10-15%5-10%3-5%<3%
This Table has been developed by William P. Fisher, Jr. based on the Rasch literature and his many years of experience conducting Rasch analyses in different settings.

* How far the average or modal measure is from the center of the item calibrations. Just as a rough indication, if the average measure is less than one error of measurement from the center of the item hierarchy, then the instrument is on target. The average individual error of measurement made more sense to me to use than the SE of the mean, as this latter can be quite small. Of course, an instrument might not have items that go as far up or down the scale as the measures go, so some indication of how well the measure and calibration distributions match would also be in order.

** The variance explained by the measures in a Principal Components Analysis of the standardized residuals changes with the targeting of the items on the persons. There is no set range of values useful for assessing scale functioning. For more information, see:

Rating Scale Instrument Quality Criteria. Fisher, W.P. Jr. … Rasch Measurement Transactions, 2007, 21:1 p. 1095

This article was revised by Fisher, W.P. Jr. on 2/1/2018. The original table showed the Variance in data explained by measures as: <50%, 50-60%, 60-70%, 70-80%, and >80%.

Rasch Publications
Rasch Measurement Transactions (free, online) Rasch Measurement research papers (free, online) Probabilistic Models for Some Intelligence and Attainment Tests, Georg Rasch Applying the Rasch Model 3rd. Ed., Bond & Fox Best Test Design, Wright & Stone
Rating Scale Analysis, Wright & Masters Introduction to Rasch Measurement, E. Smith & R. Smith Introduction to Many-Facet Rasch Measurement, Thomas Eckes Invariant Measurement: Using Rasch Models in the Social, Behavioral, and Health Sciences, George Engelhard, Jr. Statistical Analyses for Language Testers, Rita Green
Rasch Models: Foundations, Recent Developments, and Applications, Fischer & Molenaar Journal of Applied Measurement Rasch models for measurement, David Andrich Constructing Measures, Mark Wilson Rasch Analysis in the Human Sciences, Boone, Stave, Yale
in Spanish: Análisis de Rasch para todos, Agustín Tristán Mediciones, Posicionamientos y Diagnósticos Competitivos, Juan Ramón Oreja Rodríguez

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