This (unidimensional) dataset includes three parameter logistic model (3PL) item parameter estimates for two groups. The Form X items are from a "new" form and the Form Y items are from an "old" form. The data are listed in Table 6.5 in Test Equating, Scaling, and Linking (2nd ed.). There are 12 common items between the two forms.
A list of length two. The first element
pars is a list of length two.
Each of the list elements in
pars is a 36 x 3 matrix of item parameters.
Element one is for
Form X, and element two is for
The second list element in
KB04 is a matrix identifying the common items
between the two sets of parameters in
pars. That is, the first column in
common identifies the rows in
pars$form.x that are common items.
The second column identifies the corresponding set of common items in
In the book, the authors transform the Form X parameters to the Form Y scale.
Kolen, M. J., & Brennan, R. L. (2004) Test Equating, Scaling, and Linking. (2nd ed.), p. 192 New York: Springer
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