The recovery of the density scale using a stochastic quasi-realization of additive conjoint measurement.
This paper attempts to illuminate some of the practical limitations that the Rasch model (and by extension, Item Response Theory models) may have by focusing on the recovery of the density scale. Five simulation trials were conducted: the first four to recover the density scale with different deviations from the assumptions implicit in the use of the Rasch model and the fifth trial with an almost ideal data set. Results demonstrate that when error distributions are insufficient the results may be ordinal at best, and when error distributions are non-symmetrical, the positions of items may be biased with respect to the positions of persons. Results also confirm that errors of estimation, and test and sample information functions are sample dependent.
Pelton
Timothy W
TW
Department of Curriculum and Instruction, University of Victoria, PO Box 3010 STN CSC, Victoria, British Columbia, Canada V8W 3N4. tpelton@uvic.ca
Bunderson
C Victor
CV
D015982:Bias; D002170:Canada; D006801:Humans; D015233:Models, Statistical; D055585:Physical Phenomena; D010825:Physics; D011336:Probability; D011594:Psychometrics / Q000379:methods* / Q000706:statistics & numerical data; D013269:Stochastic Processes; D014894:Weights and Measures