﻿ Unmeasurable

# Unmeasurable

If an element is reported as "Unmeasurable" in Table 7 or Status "-4" in a Score file, then ...

Observations for the element are part of an extreme score. One way is to impute non-extreme elements.

For instance:

Original specifications and data:

Models = ?, ?, R5 ; persons, items, rating-scale is 1-5

Data =

1, 1-2,  3, 4

2, 1-2,  3, 2

3, 1-2,  5, 5

4, 1-2.  1, 2

Person 3 is reported as "Unmeasurable". This is because it is the only person element rated 5, and all its ratings are 5. We know that 5 is better than 4, but the data do not tell us how much.

Let's say that 5 is only a little better than 4. Then we impute observations of 4 to Person 3:

Models =

3, ?, RScale, 0.5  ; weight observations of 3 at o.5

?, ?, RScale ; everyone else remains as before

*

Rating-scale = RScale, R5, General  ; Person 3 and everyone else share the same rating scale

Data =

1, 1-2,  3, 4

2, 1-2,  3, 2

3, 1-2,  5, 5  ; original data, now weighted 0.5

3, 1-2,  4, 4  ; imputed data, now weighted 0.5

4, 1-2.  1, 2

Person 3 will now be estimated with a measure corresponding to a rating of 4.5

Help for Facets Rasch Measurement Software: www.winsteps.com Author: John Michael Linacre.

The Languages of Love: draw a map of yours!

 Forum Rasch Measurement Forum to discuss any Rasch-related topic

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 with Raters and Rating Scales: Rasch Models for Rater-Mediated Assessments, George Engelhard, Jr. & Stefanie Wind 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
Winsteps Tutorials Facets Tutorials Rasch Discussion Groups

Coming Winsteps & Facets Events
May 22 - 24, 2018, Tues.-Thur. EALTA 2018 pre-conference workshop (Introduction to Rasch measurement using WINSTEPS and FACETS, Thomas Eckes & Frank Weiss-Motz), https://ealta2018.testdaf.de
May 25 - June 22, 2018, Fri.-Fri. On-line workshop: Practical Rasch Measurement - Core Topics (E. Smith, Winsteps), www.statistics.com
June 27 - 29, 2018, Wed.-Fri. Measurement at the Crossroads: History, philosophy and sociology of measurement, Paris, France., https://measurement2018.sciencesconf.org
June 29 - July 27, 2018, Fri.-Fri. On-line workshop: Practical Rasch Measurement - Further Topics (E. Smith, Winsteps), www.statistics.com
July 25 - July 27, 2018, Wed.-Fri. Pacific-Rim Objective Measurement Symposium (PROMS), (Preconference workshops July 23-24, 2018) Fudan University, Shanghai, China "Applying Rasch Measurement in Language Assessment and across the Human Sciences" www.promsociety.org
Aug. 10 - Sept. 7, 2018, Fri.-Fri. On-line workshop: Many-Facet Rasch Measurement (E. Smith, Facets), www.statistics.com
Oct. 12 - Nov. 9, 2018, Fri.-Fri. On-line workshop: Practical Rasch Measurement - Core Topics (E. Smith, Winsteps), www.statistics.com

Our current URL is www.winsteps.com