Description Usage Arguments Parameter Description
Adds item response theory model fits to an mcTestAnalysisData object,
using the ltm
package.
1 | addIRTfits(mctd)
|
mctd |
Existing mcTestAnalysis data object |
Difficulty. The difficulty parameter, β, 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, α,
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, γ, is included in the
3PL model, in addition the previous parameters, and reflects the influence
of guessing for each item. Uses tpm
from ltm
.
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