Adds item response theory model fits to an mcTestAnalysisData object, using the ltm package.




Existing mcTestAnalysis data object

Parameter Description

Difficulty. The difficulty parameter, \(\beta\), sometimes called the threshold parameter, describes the difficulty of a given item. It is the only parameter estimated in the 1PL (Rasch) model. Uses rasch from ltm.

Discrimination. The discrimination parameter, \(\alpha\), reflects the effectiveness of the item in differentiating between high- and low-performing students. This parameter is estimated in the 2PL model, in addition to difficulty. Uses ltm from ltm.

Guessing. The guessing parameter, \(\gamma\), is included in the 3PL model, in addition the previous parameters, and reflects the influence of guessing for each item. Uses tpm from ltm.