Item information and discrimination functions for trinary PCM items

Wies Akkermans, Eiji Muraki

    Research output: Contribution to journalArticleAcademicpeer-review

    6 Citations (Scopus)
    110 Downloads (Pure)


    For trinary partial credit items the shape of the item information and the item discrimination function is examined in relation to the item parameters. In particular, it is shown that these functions are unimodal if δ2 – δ1 < 4 ln 2 and bimodal otherwise. The locations and values of the maxima are derived. Furthermore, it is demonstrated that the value of the maximum is decreasing in δ2 – δ1. Consequently, the maximum of a unimodal item information function is always larger than the maximum of a bimodal one, and similarly for the item discrimination function.
    Original languageEnglish
    Pages (from-to)569-578
    Number of pages10
    Issue number4
    Publication statusPublished - 1997


    • Partial credit model
    • Trinary items
    • Item information function
    • Item discrimination function
    • Maximum item information


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