Constant Information Model, a New, Promising Item Characteristic Function.
TENNESSEE UNIV KNOXVILLE DEPT OF PSYCHOLOGY
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The methods and approaches introduced so far for estimating the operating characteristics of item response categories require the Old Test, or a set of items, whose operating characteristics are known. To generalize these methods to apply for the situation where we start to develop a new item pool, i.e., there is no Old Test, an approach is made by assuming that the tentative item pool has a substantial number of equivalent items, even though their common item characteristic function is not known yet. It is observed that, within the type of item characteristic function which is strictly increasing in the latent trait, Theta, with zero and unity as its two asymptotes, the area under the square root of the item information function is a constant value, pi. The item characteristic function which provides a constant item information is searched and discovered, and is named the constant information model. Using this model, it is observed that the subset of equivalent binary items can be used as a substitute for the Old Test, and those methods and approaches are generalized in the present situation. It is discovered that, for once, items with low discrimination power have a significant role. Author
- Statistics and Probability