FURTHER RESULTS ON THE STANDARD ERRORS OF ESTIMATE ASSOCIATED WITH ITEM-EXAMINEE SAMPLING PROCEDURES

Defining one observation as the score received by one examinee on one item, the results of this investigation suggest that, for a given test length, item-examinee sampling procedures having the same number of observation have, for all practical purposes, the same standard error in estimating μ but different standard errors in estimating σ. Additionally, the variance of the item difficulty indices (proportion answering the item correctly) was found to be a significant factor in accounting for differences in standard errors of estimating μ between normative distributions differing primarily in degree of skewness.