Document Type : Research Manuscript


national organization for educational testing


Abstract: so many natural phenomena of determining relationship and the effect of input variables
on response variable in statistical studies may be different from the suggested model that the
researcher selects for his study due to the occupant exists in the structure of data. It may be so
influential on different distributions considered for response variables. The optimal properties of
estimators evaluated and studied for two statistical variables considered for response variable and
input variables in the suggested model. It has been simulated for study and real data has been also
investigated. The results confirmed the superiority of a model which is close to the structure of the