In unanchored analyses, the item difficulties are centered by UIMEAN= or the person abilities are centered by UPMEAN=.
UEXTREME = No (the default). Do not include items or persons with extreme scores (minimum possible or maximum possible) when computing the centering.
UEXTREME = Yes. Do include items or persons with extreme scores (minimum possible or maximum possible) when computing the centering.
Example: using Exam1..txt
UIMEAN=0 and UEXTREME=No (items with extreme scores excluded when setting the local origin at zero)
SUMMARY OF 14 MEASURED (NON-EXTREME) TAP
-------------------------------------------------------------------------------
| TOTAL MODEL INFIT OUTFIT |
| SCORE COUNT MEASURE ERROR MNSQ ZSTD MNSQ ZSTD |
|-----------------------------------------------------------------------------|
| MEAN 16.9 35.0 .00 .71 .96 .0 .68 -.1 |
| P.SD 12.9 .0 3.48 .21 .28 .7 .58 .5 |
| MAX. 32.0 35.0 4.80 1.07 1.56 1.2 2.21 1.1 |
| MIN. 1.0 35.0 -4.40 .45 .59 -1.3 .11 -.6 |
|-----------------------------------------------------------------------------|
SUMMARY OF 18 MEASURED (EXTREME AND NON-EXTREME) TAP
-------------------------------------------------------------------------------
| TOTAL MODEL INFIT OUTFIT |
| SCORE COUNT MEASURE ERROR MNSQ ZSTD MNSQ ZSTD |
|-----------------------------------------------------------------------------|
| MEAN 18.9 35.0 -.76 .96 |
| P.SD 14.0 .0 4.26 .51 |
| MAX. 35.0 35.0 6.13 1.85 |
| MIN. .0 35.0 -6.59 .45 .59 -1.3 .11 -.6 |
|-----------------------------------------------------------------------------|
UIMEAN=0 and UEXTREME=YES (items with extreme scores included when setting the local origin at zero)
SUMMARY OF 14 MEASURED (NON-EXTREME) TAP
-------------------------------------------------------------------------------
| TOTAL MODEL INFIT OUTFIT |
| SCORE COUNT MEASURE ERROR MNSQ ZSTD MNSQ ZSTD |
|-----------------------------------------------------------------------------|
| MEAN 16.9 35.0 .75 .71 .96 .0 .68 -.1 |
| P.SD 12.9 .0 3.46 .21 .27 .7 .57 .5 |
| MAX. 32.0 35.0 5.53 1.07 1.55 1.2 2.16 1.1 |
| MIN. 1.0 35.0 -3.63 .45 .59 -1.4 .11 -.6 |
|-----------------------------------------------------------------------------|
| REAL RMSE .77 TRUE SD 3.38 SEPARATION 4.40 TAP RELIABILITY .95 |
|MODEL RMSE .74 TRUE SD 3.38 SEPARATION 4.57 TAP RELIABILITY .95 |
| S.E. OF TAP MEAN = .96 |
-------------------------------------------------------------------------------
SUMMARY OF 18 MEASURED (EXTREME AND NON-EXTREME) TAP
-------------------------------------------------------------------------------
| TOTAL MODEL INFIT OUTFIT |
| SCORE COUNT MEASURE ERROR MNSQ ZSTD MNSQ ZSTD |
|-----------------------------------------------------------------------------|
| MEAN 18.9 35.0 .00 .96 |
| P.SD 14.0 .0 4.24 .50 |
| MAX. 35.0 35.0 6.86 1.84 |
| MIN. .0 35.0 -5.80 .45 .59 -1.4 .11 -.6 |
|-----------------------------------------------------------------------------|
