Publication date: 08/13/2020

Normal Contour Ellipsoids

A normal contour ellipsoid is a 3-dimensional ellipse that encompasses a specified portion of points. The ellipsoid is computed from a contour of the multivariate normal distribution fit to the points. The ellipsoid is a function of the means, standard deviations, and correlations of variables on the plot. See Multivariate Methods for more information about multivariate normal distributions.

When you add an ellipsoid, two formatting options are available:

Coverage changes the portion of data points covered by the ellipsoid. The larger the value, the bigger the ellipsoid.

Transparency changes the surface of the ellipsoid from transparent to opaque. The larger the value, the more opaque the ellipsoid.

The coverage and transparency options also appear in the red triangle menu after you add the ellipsoid.

When you add normal contour ellipsoids to a 3D scatterplot, you specify whether you want an ellipsoid for all of the data or for a specific group of data. The ellipsoid for each set of grouped data is color-coded to differentiate one group from another.

You display and remove normal contour ellipsoids by selecting and deselecting Normal Contour Ellipsoids from the red triangle menu.

Related Information

Example of an Ungrouped Normal Contour Ellipsoid

Example of Grouped Normal Contour Ellipsoids

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