Run | Analysis | N | Item fit residual | Person fit residual | Item-trait interaction | PSI | Unidimensionality T-tests | |||
---|---|---|---|---|---|---|---|---|---|---|
Mean | SD | Mean | SD | χ2 (df) | P | % of significant tests | ||||
1 | Initial analysis | 109 | 0.168 | 1.824 | − 0.152 | 1.741 | 179.04 (58) | < 0.001 | 0.959 | 19.27% |
2 | 18 misfitting patients removed | 91 | 0.066 | 1.486 | − 0.009 | 1.169 | 153.30 (58) | < 0.001 | 0.962 | 15.38% |
3 | Items grouped into two testlets | 91 | − 0.016 | 1.964 | − 0.463 | 0.901 | 3.99 (4) | 0.407 | 0.934 | 3.30% |