Mixed models

Mixed models is part of:

  • Pro Core statistical software

  • System configuration

    • Windows:
      • Versions: 9x/Me/NT/2000/XP/Vista/Win 7
      • Excel: 97 and later
      • Processor: 32 or 64 bits
      • Hard disk: 150 Mb
    • Mac OS X:
      • OS: OS X
      • Excel: X, 2004 and 2011
      • Hard disk: 150Mb.

Benefits

  • Easy and user-friendly
    Easy and user-friendly XLSTAT is flawlessly integrated with Microsoft Excel which is the most popular spreadsheet worldwide. This integration makes it one of the simplest available tools to work with as it utilizes the same philosophy as Microsoft Excel. The program is accessible in a dedicated XLSTAT tab. The analyses are grouped into functional menus. The dialog boxes are user-friendly and setting up an analysis is straightforward.
  • Data and results shared seamlessly
    Data and results shared seamlessly One of the greatest advantages of XLSTAT is the way you can share data and results seamlessly. As the results are stored in Microsoft Excel, anyone can access them. There is no need for the receiver to have an XLSTAT license or any additional viewer which makes your team-work easier and more affordable. In addition, results are easily integrable into other Microsoft Office software such as PowerPoint, so that you can create striking presentation in minutes.
  • Modular
    Modular XLSTAT is a modular product. XLSTAT-Pro is a core statistical module of XLSTAT which includes all the mainstream functionalities in statistics and multivariate analysis. More advanced features contained in add-on modules can be added for specific applications. This way you can adapt the software to your needs making the software more cost-efficient.
  • Didactic
    Didactic The results of XLSTAT are organized by analysis and are easy to navigate. Moreover useful information is provided along with the results to assist you in your interpretation.
  • Affordable
    Affordable XLSTAT is a complete and modular analytical solution that can suit any analytical business needs. It is very reasonably priced so that the return of your investment is almost immediate. Any XLSTAT license comes with top level support and assistance.
  • Accessible - Available in many languages
    Accessible - Available in many languages We have ensured XLSTAT is accessible to everyone by making the program available in many languages, including Chinese, English, French, German, Italian, Japanese, Polish, Portuguese and Spanish.
  • Automatable and customizable
    Automatable and customizable Most of the statistical functions available in XLSTAT can be called directly from the Visual Basic window of Microsoft Excel. They can be modified and integrated to more code to fit to the specificity of your domain. Adding tables and plots as well as modifying existing outputs becomes easy. Furthermore, XLSTAT includes some special tools on the dialog boxes to generate automatically the VBA code in order to reproduce your analysis using the VBA editor or to simply load pre-set settings. This effortless automation of routine analysis will be a huge time saver on your part.

Principles of Mixed models

Mixed models are complex models based on the same principle as general linear models, such as the linear regression. They make it possible to take into account, on the one hand, the concept of repeated measurement and, on the other hand, that of random factor. The explanatory variables could be as well quantitative as qualitative. Mixed models can be used to carry out repeated measures ANOVA.

Mixed models equation

A mixed model is written as follows:

y = Xβ + Zγ + ε

where y is the dependent variable, X gathers all fixed effects (these factors are the classical OLS regression variables or the ANOVA factors), β is a vector of parameters associated with the fixed factors, Z is a matrix gathering all the random effects (factors that cannot be set as fixed), γ is a vector of parameters associated with the random effects and ε is an error vector.

Parameters are estimated using the maximum likelihood estimator. XLSTAT propose different covariance matrix between the errors within the framework of mixed models.

In addition, the interactions to be used in the model can be easily defined in XLSTAT.

Results for Mixed models in XLSTAT

XLSTAT allows computing the type I, II and III tests of the fixed effects. The principle of these tests is the same one as in the case of the linear model. Nevertheless, their calculation differs slightly.

As in classical ANOVA, in repeated measures ANOVA multiple comparisons can be performed. It is aimed at checking whether the various categories of a factor differ significantly or not. For example, in the case where four treatments are applied to plants, we want to know not only if the treatments have a significant effect, but also if the treatments have different effects. Numerous tests have been proposed for comparing the means of categories.

The majority of these tests assume that the sample is normally distributed. XLSTAT provides the main tests. In the case of repeated measures ANOVA, standard deviations are obtained using the maximum likelihood estimates.

Tutorials

Screenshots