Gizem UYUMAZ & Ãmay ÃOKLUKâBÃKEOÄLU
In Cognitive Diagnosis Models, every item in the measurement tool has a different effect (which is determined based on the attribute tested) on the classification of individuals in terms of attributes tested. One of the most effective factors that affects the quality of implications and the accuracy of classification, is to develop proper item?attribute relationships, in other words, the correctness of Q?matrix Misspecification of the Q?matrix leads to incorrect decisions about the individuals. The present study, serving as a fundamental research, investigates the effect of the Q?matrix misspecification in the DINA model on parameter estimations in the datasets, which are designed as a simulation and have differing sample sizes (50, 100, 250, 500, and 1,000 participants) and test length (15 and 30 items). The parameter estimations were made by using Markov Chain Monte Carlo method based on Bayesian estimation. The estimations for misspecified Q?matrix have been compared to item parameters regarding the correct Q?matrix appropriate to dataset. In the case of underspecification in Q?matrix, slipping parameters for deficiently specified items and standard error values related to these; in the case of overspecification, guessing parameters related to overestimated items and standard error values related to these were overestimated. The parameter estimation is affected by the Q? matrix misspecification in all of the conditions discussed. Nevertheless, the amount of error in estimation does not show a regular differentiation in accordance with the sample size.
