ICORFILE= item residual correlation file

This writes out the Table of inter-item correlations which is the basis of the principal components analysis of residuals. The basis for the correlations is controlled by PRCOMP=.

PRCOMP=R correlates the raw residuals

PRCOMP=S correlates the standardized residuals

PRCOMP=O correlates the observations


ICORFILE=? opens a Browse window


Extreme scores: minimum possible (0) and maximum possible (perfect) person scores are omitted from the computation of the correlations. Items with extreme scores are not reported. Their correlation is 0.


Missing data: for these Winsteps substitutes their expectations when possible. For residuals and standardized residuals, these are 0. Persons with extreme scores (minimum possible or maximum possible): Winsteps drops these from the correlation computation. The reason for these choices is to make the principal components analysis of residuals as meaningful as possible.


ICORFILE= file name


Example 1: Write out the Table of inter-item residual correlations. PRCOMP=R. ICORFILE=file.txt - Then file.txt contains, for SF.txt, fixed-field columns 12 characters wide.


           1           2    -.171665

           1           3    -.144027

           1           4    -.009290

           1           5    -.103947


Example 2: When ICORFILE= is selected on the Output Files menu or MATRIX=YES, the Data Format: Matrix option can be selected:



This produces 10-character wide columns in fixed-field format

        1         2         3         4 ...

 1.000000  -.171665  -.144027  -.009290 ...

 -.171665  1.000000   .175921   .039622 ...

 -.144027   .175921  1.000000  -.101622 ...

 -.009290   .039622  -.101622  1.000000 ...

 -.103947   .099335  -.021021   .145339 ...

  .107936  -.009881  -.039799  -.109941 ...

  .108457  -.061624   .015850  -.001168 ...


Example 3: Is there a way to include extreme scores?

1. All the correlations relating to extreme scores are zero.

2. If you select ICORFILE= from the Output Files menu, and click on "matrix". You will get all pairs of non-extreme correlations.

3. You can obtain a matrix of raw or standardized response-residuals including extreme scores, by using IPMATRIX= from the Output Files menu (check the extreme score boxes). Then use this to compute the correlations with a standard statistical package etc. You will notice that the residuals for extreme scores may not be zero. This is because they are computed based on the measures shown for extreme scores in the measure Tables.

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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
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Coming Rasch-related Events
April 10-12, 2018, Tues.-Thurs. Rasch Conference: IOMW, New York, NY, www.iomw.org
April 13-17, 2018, Fri.-Tues. AERA, New York, NY, www.aera.net
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
Sept. 3 - 6, 2018, Mon.-Thurs. IMEKO World Congress, Belfast, Northern Ireland www.imeko2018.org
Oct. 12 - Nov. 9, 2018, Fri.-Fri. On-line workshop: Practical Rasch Measurement - Core Topics (E. Smith, Winsteps), www.statistics.com



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