tpmCat | R Documentation |
This function fits Birnbaum's three parameter model for binary data and populates the fitted values for discrimination, difficulty, and guessing parameters to an object of class Cat
.
## S4 method for signature 'data.frame'
tpmCat(data, quadraturePoints = 21, ...)
## S4 method for signature 'tpm'
tpmCat(data, quadraturePoints = NULL, ...)
data |
A data frame of manifest variables or an object of class |
quadraturePoints |
A numeric to be passed into the |
... |
arguments to be passed to methods. For more details about the arguments, see |
The data
argument of the function tpmCat
is either a data frame or an object of class tpm
from the ltm
package. If it is a data frame each row represents a respondent and each column represents a question item. If it is an object of the class tpm
, it is output from the tpm
function in the ltm
package.
The quadraturePoints
argument of the function tpmCat
is used only when the data
argument is a data frame. quadraturePoints
is then passed to the tpm
function from the ltm
package when fitting Birnbaum's three parameter model to the data and is used when approximating the value of integrals.
The function tpmCat
returns an object of class Cat
with changes to the following slots:
difficulty
A vector consisting of difficulty parameters for each item.
discrimination
A vector consisting of discrimination parameters for each item.
model
The string "tpm"
, indicating this Cat
object corresponds to Birnbaum's three parameter model.
See Cat-class
for default values of Cat
object slots. See Examples and setters
for example code to change slot values.
In case the Hessian matrix at convergence is not positive definite try to use start.val = "random"
.
Haley Acevedo, Ryden Butler, Josh W. Cutler, Matt Malis, Jacob M. Montgomery, Tom Wilkinson, Erin Rossiter, Min Hee Seo, Alex Weil
Baker, Frank B. and Seock-Ho Kim. 2004. Item Response Theory: Parameter Estimation Techniques. New York: Marcel Dekker.
Birnbaum, Allan. 1968. Some Latent Trait Models and their Use in Inferring an Examinee's Ability. In F. M. Lord and M. R. Novick (Eds.), Statistical Theories of Mental Test Scores, 397-479. Reading, MA: Addison-Wesley.
Rizopoulos, Dimitris. 2006. “ltm: An R Package for Latent Variable Modeling and Item Response Theory Analyses." Journal of Statistical Software 17(5):1-25.
Cat-class
, ltmCat
, polknowMT
, probability
## Creating Cat objects from large datasets is computationally expensive
## Load the Cat object created from the above code
data(tpm_cat)
## Slots that have changed from default values
getModel(tpm_cat)
getDifficulty(tpm_cat)
getDiscrimination(tpm_cat)
## Changing slots from default values
setEstimation(tpm_cat) <- "MLE"
setSelection(tpm_cat) <- "MFI"
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