New Features

New in IRTPRO™ Version 6

IRTPRO™ 6 academic license holders now have access to a trial version of flexMIRT® for evaluation purposes and to cross-train students on flexMIRT® syntax. You may open a *.flexMIRT syntax file directly from within IRTPRO™ and run the analysis. The trial engine of flexMIRT included in IRTPRO™ 6 is for teaching and evaluation purposes.

You will notice that the trial version is capacity-restricted in the following manner:

  • The maximum number of items is 20 in trial version.
  • Multilevel analysis is not available in trial version.
  • The maximum number of groups is 2 in trial version.
  • There is a sample size limit of 1,500 per group.
  • Only the Bock-Aitkin EM algorithm is available in trial version.
  • Classical item statistics mode is not available in trial version.
  • Simulation mode is not available in trial version.
  • The engine is single-threaded.
  • Only Basic level GOF stats are available.
  • No M2 family goodness-of-fit indices are available.

Additional changes:

  • Tabbed child windows have been added, along with an output panel to display additional information.
  • improved scaling functionality to support UHD display resolution
  • bug fixes

You may also download flexMIRT® examples or IRTPRO™ examples from here.

IRTPRO™ Version 5.1

IRTPRO™ 5.1 now includes a new ICC/TIF plot display control option for univariate models. The

Plot Theta = n

keyword has been added to the Miscellaneous command syntax and is accessible in the GUI via the Analysis, Advanced Options option from the main menu. Previously, the X-axis of graphs were automatically set to display values between -3 and 3 for these graphs. By setting n to the user’s integer of choice, the range of this axis can now be adjusted.

IRTPRO™ Version 5.0

A brand new subscription-based delivery and support model

After paying for a renewable Academic or Standard subscription, you are entitled to download three (3) concurrent installs (previously offered single-user IRTPRO™ licenses only allow one install), access to all upgrades or updates, technical support, and discounts on subscriptions for other VPG or SSI programs, as long as your subscription is active. Additional installs can be added easily at any time at substantially lower cost. Unlike perpetually installed and activated software, you may move licenses or activations from one machine to another from your VPG account. This may be particularly convenient given increased remote work demands placed on all of us. Educator (or workshop instructor) access to fully-functioning student licenses are available at no additional cost if the instructor maintains an active IRTPRO™ Academic or Standard subscription. Even more affordable IRTPRO™ Basic subscriptions are available.

Handling of missing data when importing text data such as .csv files

While importing text data, IRTPRO™ 5.0 uses the first 50 non-blank lines to determine the data type. During this check, as long as any cell is found to be numeric data, that column is assume numeric. In the previous code, once string data is found, the column is assumed to be character type which is converted to the numeric value of 0.
In the previous IRTPRO™ version, only an empty field (two consecutive commas separated by zero or more spaces) is recognized as a missing data value and coded as -1, the default missing data code. In IRTPRO™ 5.0, the string patterns “NA” and “NIL” are also recognized as missing data. These special patterns are case insensitive, as shown below.


Use of Stat/Transfer Version 15 to ensure import/export compatibility with software packages such as SPSS, SAS and STATA

The data import feature has been upgraded from Stat/Transfer Version 14 to the most recently released Version 15. Among others, Stat/Transfer supports importing data from the most current SAS, SPSS, STATA, MINITAB, MATLAB and R software.

Ability to facilitate the automatic generation of syntax files using a third-party program.

In production use, researchers often have to analyze data that consist of a very large number of items often in excess of 200. Using IRTPRO™ 5.0 a list of items that are specified in the order they occur in the dataset can be simplified using the “-“ symbol.
IRTPRO™ supports item range, for example, Item1-Item45 on the following commands:

Items, Codes, Model, BFA

Suppose, for example, that the items Calm, Tense, Regretful, AtEase, Anxious, and Nervous appear in that order in an IRTPRO™ (.ssig) data file, then

Codes(Calm) = 0(0), 1(1), 2(2), 3(3), 4(4);
Codes(Tense) = 0(0), 1(1), 2(2), 3(3), 4(4);
Codes(Regretful) = 0(0), 1(1), 2(2), 3(3), 4(4);
Codes(AtEase) = 0(0), 1(1), 2(2), 3(3), 4(4);
Codes(Anxious) = 0(0), 1(1), 2(2), 3(3), 4(4);
Codes(Nervous) = 0(0), 1(1), 2(2), 3(3), 4(4);

Can be written as

Codes(Calm-Nervous) = 0(0), 1(1), 2(2), 3(3), 4(4);

IRTPRO™ Version 4.2

The data import feature

The data import feature has been upgraded from Stat/Transfer Version 13 to the most recently released Version 14. Among others, Stat/Transfer Version 14 has added support for Stata 15/MP.

Copying IRT graphs

To facilitate copying IRT graphs to, for example, an MS Word document, the user just have to click on the appropriate graph to enable a context menu that lists “Copy Chart”. See the revised IRTPRO™ FAQ document.

IRTPRO™ Version 4.1

Correct display of Id number during scoring

When Scoring is requested, an internal id is always printed, and if the user selects an ID variable, it’s also printed to the –sco.txt file. If the user-selected ID is the first column of the IRTPRO™ spreadsheet (.ssig file) in IRTPRO™ version 4.0, then the ID-values are not displayed. This problem has been fixed.

Correct specification of the number of processors

In IRTPRO™ version 4.0 it may occur that when more than one processor is specified via the miscellaneous tab, only a single processor is used. This issue has been fixed.

Use of ASCII2SSIG64 utility

When using the ASCII2SSIG64 utility to create .SSIG files, the ASCII files had to use -1 to denote missing values. An option /missing <value> has been added in case the user wants to use a different value (for example -999) to denote missing values. See the revised IRTPRO™ FAQ document.

Improved edit function

In IRTPRO™ version 4.1 a number of changes have been made to the edit function. Note however, if a user makes changes to a syntax (.irtpro) file, the following steps need to be used.

  • Save the changes.
  • Close the relevant file.
  • Open the file to ensure that the changes made are correctly loaded into the dialogs.

Problem with FixedTheta statement corrected

In IRTPRO™version 4.0, if the default estimation method is BAEM (for example) and if the user changes this via the Options (or Advanced Options) window to MH-RM, then an error is generated as a result of the statement FixedTheta =; which is added to the MH-RM options. This problem has been fixed.