Description Usage Arguments Details Value Methods (by class) See Also Examples
This function allows the application of various methods for the detection of differential item functioning in multistage tests. Currently five methods are implemented: 1. Logistic Regression, 2. mstSIB, 3. analytical scorebase tests, 4. a scorebased Bootstrap test, 5. a scorebased permutation test. The required input differs with regard to the selected DIF test.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16  ## Default S3 method:
mstDIF(resp, DIF_covariate, method, theta = NULL, see = NULL, ...)
## S3 method for class 'AllModelClass'
mstDIF(
object,
DIF_covariate,
method,
theta = NULL,
see = NULL,
theta_method = "WLE",
...
)
## S3 method for class 'dRm'
mstDIF(object, DIF_covariate, method, theta = NULL, see = NULL, ...)

resp, object 
A data frame or matrix containing the response matrix. Rows correspond to respondents, columns to items. Or an object of class SingleGroupclass or MultiGroupclass object as returned by mirt, or a dRm object as returned by the RM function in eRm. 
DIF_covariate 
A vector of ability estimates for each respondent. 
method 
A character value indicating the DIF test that should be used. Possible values are "logreg" (Logistic regression), "mstsib" (mstSIB), "bootstrap" (scorebased Bootstrap test), "permutation" (scorebased) permutation test) and "analytical" (analytical scorebased test). 
theta 
Estimates of the ability parameters. 
see 
Estimates of the standard error of estimation. 
... 
Additional, testspecific arguments. 
theta_method 
Method for estimating the ability parameters if they should be estimated based on the responses. The calculation is carried out by the mirt package. Can be: "WLE" (default), "MAP", "EAP", "ML", "EAPsum", "plausible", "classify". 
Author: Rudolf Debelak and Dries Debeer
An object of class mstDIF
, which is a list with the following elements:
resp
The response matrix as a data frame.
method
The used DIF detection method.
test
The used test or statistic.
DIF_covariate
The person covariate tested for DIF.
DIF_test
A list with the DIFtest results.
call
The function call.
method_results
The complete output of the selected DIF test. Differs depending on the selection.
default
: Default mstDIF method
AllModelClass
: mstDIF method for mirtobjects
dRm
: mstDIF method for dRmobjects
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20  ## load data
data("toydata")
resp < toydata$resp
group_categ < factor(toydata$group_categ)
theta_est < toydata$theta_est
see_est < toydata$see_est
## test DIF along a categorical covariate (a factor) using the
## logistic regression method
res1 < mstDIF(resp, DIF_covariate = group_categ, method = "logreg",
theta = theta_est)
res1
summary(res1)
## test DIF along a categorical covariate (a factor) using the
## mstSIB method
res2 < mstDIF(resp, DIF_covariate = factor(group_categ), method = "mstsib",
theta = theta_est, see = see_est)
res2
summary(res2)

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