Best Procedures For Sample-Free Item Analysis

Abstract

Wright's (1969) widely used "unconditional" pro cedure for Rasch sample-free item calibration is biased. A correction factor which makes the bias negligible is identified and demonstrated. Since this procedure, in spite of its superiority over "condi tional" procedures, is nevertheless slow at calibra ting 60 or more items, a simple approximation which produces comparable estimates in a few seconds is developed. Since no procedure works on data containing persons or items with infinite para meter estimates, an editing algorithm for preparing item response data for calibration is appended.