This chapter addresses each of the following research questions, with an explanation of how the output can be used to find answers: What is the spread of item difficulties (and category difficulties, for polytomous items)? How discriminating is each item? What is the distribution of abilities/traits in this group of examinees/respondents? How does the ability distribution compare to the item difficulty distribution? How much information does the test provide over the ability/trait range? How does each item contribute to the test information? and For a given population or sample distribution, how reliable are the ability/trait estimates? Most of the questions relate to the item or examinee parameter estimates. Before examining how the questions can be answered, a brief, conceptual explanation of parameter estimation is given. In addition, write-ups are presented for the results for an analysis of dichotomous and polytomous items. Comments on the write-up and further explanations are provided following the example report. In general, the examples show some of the ways that the results could be described in a report.
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