Assessing the assumption of multivariate normality is required by many parametric multivariate statistical methods, such as MANOVA, linear discriminant analysis, principal component analysis, canonical correlation, etc. It is important to assess multivariate normality in order to proceed with such statistical methods. There are many analytical methods proposed for checking multivariate normality. However, deciding which method to use is a challenging process, since each method may give different results under certain conditions. Hence, we may say that there is no best method, which is valid under any condition, for normality checking. In addition to numerical results, it is very useful to use graphical methods to decide on multivariate normality. Combining the numerical results from several methods with graphical approaches can be useful and provide more reliable decisions.

Here, we present a web-tool application to assess multivariate normality. This application uses the MVN package from R. This tool contains the three most widely used multivariate normality tests, including Mardia’s, Henze-Zirkler’s and Royston’s, and graphical approaches, including chi-square Q-Q, perspective and contour plots (*Multivariate analysis tab*). It also includes two multivariate outlier detection methods, which are based on robust Mahalanobis distances (*Outlier detection tab*). Moreover, this web-tool performs the univariate normality of marginal distributions through both tests and plots (*Univariate analysis tab*). More detailed information about the tests, graphical approaches and their implementations through this web-tool and MVN package can be found in the paper of the package. All source codes are in GitHub.

In order to use this application,

(i) load your data set using **Data upload** tab. If data set has a group variable, users can define whether this variable is in the first or last column then the analysis will be performed in each sub-group,

(ii) check univariate normality through univariate normality tests and plots in the **Univariate analysis** tab. Users also can get descriptive statistics using this tab,

(iii) check multivariate outliers in the **Outlier detection** tab,

(iv) check multivariate normality through MVN tests and plots in the **Multivariate analysis** tab.

Users can download univariate results (both descriptive statistics and univariate normality tests, as txt) and univariate plots (as pdf) from **Univariate analysis** tab, outlier set (as txt), data set without outliers (as txt) and chi-square QQ plot (as pdf) from **Outlier detection** tab, also MVN test results (as txt) and plots (as pdf or png) can be downloaded by using **Multivariate analysis** tab.

**Please note that box-plots are based on standardized values (centered and scaled), and perspective and contour plots are only available for bivariate normal distributions.**

**If there are missing values in the data, a listwise deletion will be applied and a complete-case analysis will be performed.**

Hacettepe University Faculty of Medicine Department of Biostatistics

selcuk.korkmaz@hacettepe.edu.tr

Hacettepe University Faculty of Medicine Department of Biostatistics

dincer.goksuluk@hacettepe.edu.tr

Hacettepe University Faculty of Medicine Department of Biostatistics

gokmen.zararsiz@hacettepe.edu.tr

Marmara University Faculty of Arts and Sciences Department of Physics

Istanbul University Faculty of Science Department of Biology

(1) Advanced options have been added for both perspective and contour plots.

(1) Advanced options have been added for the multivariate outlier detection.

(2) Bug fixes.

(1) MVN paper published at The R Journal. The complete reference information is at the **Citation** tab

(2) Minor improvements and fixes.

Univariate descriptive statistics, tests and plots have been added.

MVN web-tool presented at 16th National Biostatistics Congress in Antalya.

(1) Sub-group analysis has been added.

(1) Three different outlier detection methods, including Mahalanobis distance, adjusted quantile and PCOut, are available now.

(2) New data set without outliers can be downloaded.

(1) Web-tool version of the MVN package has been released.

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