The Effect of Sample Size and Different Ability Distribution on Item Parameters Utilizing Three Logistic Model

Abstract

This study aimed at verifying the effect of Sample Size and the ability distribution (normal, positive and negative skewed) on item parameters, To achieve the aim of the study, generating responses to the nine groups of subjects according to three parameter logistic model using WINGEN program on 50 dichotomous items, The responses of the examinees were analyzed by BILOG– MG 3 programs for each group, The results of the repeated measurement ANOVA revealed that there were statistical significant differences between difficulty means and discrimination means attributed to Sample Size, The results also revealed that there were statistical significant differences between difficulty means and discrimination means attributed to ability distribution.