Authors: Adams, R.J, Wu, M.L, and Wilson, M.R. (2015)

Publisher: ACER   
ACER ConQuest 4 is a computer program for fitting both unidimensional and multidimensional item response and latent regression models. It provides data analysis based on a comprehensive and flexible range of item response models (IRM), allowing examination of the properties of performance assessments, traditional assessments and rating scales. ACER ConQuest 4 also offers wider measurement and research community analysis procedures based on the most up-to-date psychometric methods of multifaceted item response models, multidimensional item response models, latent regression models and drawing plausible values.

Bibliographic reference:
Adams, R. J., Wu, M. L., & Wilson, M. R. (2015). ACER ConQuest: Generalised Item Response Modelling Software [Computer software]. Version 4. Camberwell, Victoria: Australian Council for Educational Research.

The ACER ConQuest Version 4 software includes:

  • Estimation of the Bradley–Terry–Luce (BTL) model for pairwise comparisons
  • A choice of marginal maximum likelihood or joint maximum likelihood estimation
  • Fitting of a multidimensional and multifaceted form of Bock’s nominal response model, including its special cases, the two parameter logistic (2PL) model and generalised partial credit model
  • Direct reading of SPSS system files
  • Output of results to SPSS or EXCEL files
  • A wide array of graphical outputs, including Wright maps and Wright predicted probability maps
  • Person fit and residuals
  • Latent variable path modelling
  • Mantel-Haenszel DIF estimates

The ACER ConQuest Version 4 has the following new features:

  • Implementation of multidimensional and multifaceted Bock model and generalised partial credit model (GPCM)
  • Addition of matrix variables
  • Matrix manipulation functions: compute, for, if and while commands to manipulate matrices
  • Functionality to create likelihood plots
  • Functionality to create information maps

The ACER ConQuest 4 software update includes bug fixes.

Release notes:

Version 4.13

  • Mac version released: console version for 64-bit Mac OS.
  • Added functionality to request command history SET STORECOMMANDS=YES/NO. The history can be written on the console or redirected to a file via CHISTORY command.
  • Group option in DESCRIPTIVES, FIT, ITANAL, KIDMAP commands can now handle nested groups (e.g., gender by country). The maximum categories per group has been increased from 100 to 1000.
  • Improved KIDMAP outputs.
  • Multiple bug fixes.

Version 4.5

  • The centre=?  option for generate can now be "cases", "items", "yes" or "no".  Yes is the same as item centering.
  • LET command special characters '/' an '$' have been dropped and it is ok to use '=' and ',' in a let.  The '|' remains as a special character so that ';' can  be entered. "~" is an illegal character and cannot be used in any syntax or variables names.
  • An option decimals=?  can be added to the print command to control the number of decimal places for numbers in the display.
  • Both the print and scatter arguments can now be either matrix variables or a valid "compute" expression that returns a matrix variable.
  • A set of 6 logical operators have been added  for use in compute  "==",  "!=", "<=", ">=", ">", and "<".  These operators are applied element-wise to a  pair of matrices and return  matrices of '1' and '0' with 1 if an element wise comparison is true and 0 if false.
  • A new matrix manipulation function iif that takes three arguments (eg iif(x,y,z)).  All three arguments must be matrices of the same dimensions.  The result  is a matrix where an element takes its value from the second argument if the matching element is '1' in the first argument, otherwise it takes is value from the second argument.
  • The matrixout option, when used with itanal, provides a matrix of plausible variable means and standard deviations.
  • Fixed display of Table 7 in show file if it is requested as an Excel file.
  • Table 9 in show file no longer displayed as default when model is unidimensional.
  • Multiple bug fixes.

Version 4.2
Added uniquepid=yes option in SET command, drastically reducing the processing time for datasets with unique PIDs (i.e., each record corresponds to only one case and only one PID)

Version 4.1
Added instructor/academic licence option (Standard licence with time limit for academic use).

Added INFOMAP to the Plot menu item. This enables GUI manipulation of the INFOMAP option in Plot.

To download the installer/trial version and/or purchase licence keys, please visit the ACER shop at:


Further information, queries and technical support:
For sales queries, please view the ACER ConQuest FAQ or email sales@acer.org.
For technical support, please view the ACER ConQuest Forum or email conquest@acer.org.

Free legacy software