THE EFFECT OF CRITERION SCORE GROUPING UPON ITEM PARAMETER ESTIMATION
Frank B. Baker · British Journal of Mathematical and Statistical Psychology · 1967
The differential effect of three grouping procedures upon the first two moments of the sampling distributions of the parameters X 50 and β of the item characteristic curve were investigated empirically. The results of the study indicated that differences in the variances of β and X 50 as well as in the bias of X 50 could be attributed to differences in grouping procedures. Item parameter estimates possessing the minimum bias and variance within the study were those yielded by the grouping procedure which used equally spaced criterion score intervals and the same number of subjects within each interval.