Package: tppcm
Type: Package
Title: Step Discriminations for the Two-Parameter Partial Credit Model
        on Top of 'TAM'
Version: 0.1.0
Authors@R: person("Jie-Wen", "Tsai", email = "tsai.jiewen@gmail.com", role = c("aut", "cre"))
Description: In the two-parameter partial credit model (TPPCM) of Yu (1991)
    <https://hdl.handle.net/2142/21459>, every step of a polytomous item has
    its own discrimination. Estimation is left to existing software: 'TAM'
    (tam.mml.3pl() with a step design matrix, tam.mml.2pl(), tam.mml()) and,
    for the bilinear product form and non-negativity constraints, 'sirt'
    (xxirt()). The package adds what these packages do not provide: standard
    errors of step discriminations based on the full observed information,
    step-level Wald tests, and score tests with modification indices and
    expected parameter changes for moving down the model ladder saturated
    TPPCM -> product form -> generalized partial credit model -> partial
    credit model, limited-information fit statistics (the M2 statistic, root
    mean square error of approximation, standardized root mean squared
    residual, comparative fit index and Tucker-Lewis index; Maydeu-Olivares
    and Joe (2006) <doi:10.1007/s11336-005-1295-9>) for any step design, step
    contributions to the item information, and tests of differential step
    functioning across groups: per-step Lagrange multiplier tests from one
    multigroup fit (Glas (1998)
    <https://www3.stat.sinica.edu.tw/statistica/j8n3/j8n32/j8n32.htm>), with
    the generalized score test of Boos (1992)
    <doi:10.1080/00031305.1992.10475921>, likelihood ratio tests with
    configural, metric, scalar and partial multigroup designs, score-based
    tests (Merkle and Zeileis (2013) <doi:10.1007/s11336-012-9302-4>) and
    model-based trees (Zeileis, Hothorn and Hornik (2008)
    <doi:10.1198/106186008X319331>). The generalized partial credit model of
    Muraki (1992) <doi:10.1177/014662169201600206> is the special case with
    equal steps within items.
License: GPL (>= 2)
URL: https://github.com/jiewenTsai/tppcm
BugReports: https://github.com/jiewenTsai/tppcm/issues
Encoding: UTF-8
Language: en-US
Depends: R (>= 4.1), TAM
Imports: CDM, graphics, MASS, sirt, stats
Suggests: knitr, mirt, numDeriv, partykit, psychotools, psychotree,
        rmarkdown, strucchange, testthat (>= 3.0.0)
VignetteBuilder: knitr
Config/testthat/edition: 3
RoxygenNote: 7.3.2
NeedsCompilation: no
Packaged: 2026-10-16 13:44:45 UTC; jiewentsai
Author: Jie-Wen Tsai [aut, cre]
Maintainer: Jie-Wen Tsai <tsai.jiewen@gmail.com>
Repository: CRAN
Date/Publication: 2026-10-28 11:00:02 UTC
