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. 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. ICORFILE=file.txt - Then file.txt contains, for SF.txt,

       Item        Item        Correlation

       1        2        -.04

       1        3        .05

       .....

       2        3        -.04

       2        4        -.20

       .....

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

This produces:

 1.0000  -.0451   .0447   .0095  .....

 -.0451  1.0000  -.0448  -.2024  .....

  .0447  -.0448  1.0000  -.0437  .....

 ......  ......  ......  ......  .....

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.