Effects of Passage and Item Scrambling on Equating Relationships

Abstract

This study investigated the effects of passage and item scrambling on equipercentile and item response theory equating using a random groups design. For all four tests and for both scramblings used, differences in item and examinee statistics were found to exist between all three forms used (the base form and the two scrambled forms). Up to 50% of the examinees administered a scrambled form would have received a different scale score if the base form equating, rather than the scrambled form equating, had been used to convert their number-correct scores. It is, therefore, suggested that caution be used when scrambled forms are being administered, because in applications such as that studied here, the effects of applying the equating results obtained using a base form to the number-correct scores obtained on a scrambled form can be quite substantial in terms of the numbers of examinees who would receive different scores.