SuperMix Support

SSI, Inc. offers a technical support service via e-mail. This service is only available to registered end users of the SSI software products. Click here to view SSI’s policy and procedures for obtaining technical support.

This service applies to problems in using the software and does not include statistical consultation. If you need help with modeling concepts and interpretation, please consult our list of related material or post a question to the Multilevel Listserv. If you require statistical consultation service, Vector Psychometric Group‘s Consulting Division would be pleased to be of assistance. Contact the VPG Sales Desk at for more information.

Please note that the program may not be able to read special characters such as ė, ö, ý, ş, etc. not used in English. Users should take care to avoid the use of these in either path or file names when using SuperMix.


How can I get started with SuperMix?

Do you need guidance with setting up your SuperMix analysis? We suggest checking the online help file, which is accessed via the Contents option of the SuperMix Help menu.

Should I sort the data before running a model?

Before running a model, the data must be sorted by level 2 ID (level-2 model) and in the case of a level-3 model, IDs should be sorted in the sequence (level-3; level-2).

Why can’t I get SuperMix output?

Step 1

  •  Check version number: SuperMix 2.1. Contact SuperMix tech support if your version number and/or date are different. 
  • Check operating system.

Step 2

  •  .inp and .out files are stored in a folder with an extremely long name or non-English characters folder is write-protected
  •  running from a USB stick with too little space available for temp files.

Other notices:

  • When running SuperMix using Optimization Method: maximum posterior (Advanced tab)

The following message is written to the output file:

    **** Convergence was not attained. Results below may not be reliable.
    **** Increasing the maximum number of iterations may solve the problem.

Ignore this message if the actual number of iterations is smaller than the value specified in the Number of Iterations: text box (Configuration tab). This problem will be corrected in the first free upgrade of SuperMix.

  • Contact tech support ( to report any bugs .
  • There is a bug for mixrega.exe: contact tech support for the update.
  • Data-based graphs with missing values. 
    Currently, -9 is assumed to be a missing value code when doing data-based graphs. If -9 is a valid value for some variables, then one can change the default to the actual missing value code or to -999999 using the Settings menu when the graph is displayed.
  • Residual plots.
    Residual plots are not available for all model types. Currently, it is only available for the following cases: 
    (1) Normal continuous outcomes.
    (2) Distributions that use the log-link function.

Additional material

Continuous data

Mixed Models for Multilevel Data Analysis: An Applied Introduction

Mixed Models for Longitudinal Data: An Applied Introduction

Count data

Mixed Models for Longitudinal Count Data

Binary data

Mixed Models for Clustered Binary Outcomes

Mixed Models for Longitudinal Binary Outcomes

Ordinal and Nominal data

Mixed Models for Clustered Ordinal Outcomes

Mixed Models for Longitudinal Ordinal & Nominal Outcomes

Survival analysis example

Mixed Models for Discrete- and Grouped-Time Clustered Survival Data