The θ scale in item response theory has arbitrary unit and origin. When a group of items is calibrated twice, estimates from one calibration must be trans formed to the metric of the other. A new method is presented for doing so. It is simpler than an earlier method based on test characteristic curves, and makes more complete use of available information.
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References
1.
Lord, F.M. (1980). Applications of item response theory to practical testing problems. Hillsdale NJ: Lawrence Erlbaum.
2.
Stocking, M.L., & Lord, F.M. (1983). Developing a common metric in item response theory . Applied Psychological Measurement, 7, 201-210.
3.
Wainer, H., & Thissen, D. (1982). Some standard errors in item response theory. Psychometrika, 47, 397-412.
