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cff-version: 1.2.0
message: 'To cite package "tppcm" in publications use:'
type: software
license: GPL-2.0-or-later
title: 'tppcm: Step Discriminations for the Two-Parameter Partial Credit Model on
  Top of ''TAM'''
version: 0.1.0
abstract: '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) <https://doi.org/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) <https://doi.org/10.1080/00031305.1992.10475921>,
  likelihood ratio tests with configural, metric, scalar and partial multigroup designs,
  score-based tests (Merkle and Zeileis (2013) <https://doi.org/10.1007/s11336-012-9302-4>)
  and model-based trees (Zeileis, Hothorn and Hornik (2008) <https://doi.org/10.1198/106186008X319331>).
  The generalized partial credit model of Muraki (1992) <https://doi.org/10.1177/014662169201600206>
  is the special case with equal steps within items.'
authors:
- family-names: Tsai
  given-names: Jie-Wen
  email: tsai.jiewen@gmail.com
preferred-citation:
  type: manual
  title: 'tppcm: Step Discriminations for the Two-Parameter Partial Credit Model on
    Top of TAM'
  authors:
  - family-names: Tsai
    given-names: Jie-Wen
    email: tsai.jiewen@gmail.com
  year: '2026'
  notes: R package version 0.1.0
repository: https://cran.r-universe.dev
repository-code: https://github.com/jiewenTsai/tppcm
commit: 1168ea62adf7b6f76bc8368ac5d0188b721f9347
url: https://github.com/jiewenTsai/tppcm
date-released: '2026-10-28'
contact:
- family-names: Tsai
  given-names: Jie-Wen
  email: tsai.jiewen@gmail.com
references:
- type: thesis
  title: A Two-Parameter Partial Credit Model
  authors:
  - family-names: Yu
    given-names: Min-Ning
  institution:
    name: University of Illinois at Urbana-Champaign
  year: '1991'
  thesis-type: PhD Thesis