# Non-sphericity specification in SPM5Edit

## GUIEdit

In batch mode for factorial design specification, one can specify whether error variances are unequal across the levels of a factor and whether error variances are correlated between different levels of the same factor.

## Script, SPM.matEdit

After the design has been specified, SPM.xVi.Vi will hold a cell array of non-sphericity component matrices. Each matrix should have as many rows and columns as you have images in your design. A **1** in a certain row *i* and column *j* means that images *i* and *j* are assumed to have dependent error covariance. Note the special case if *i==j*, this encodes for the error variance of image *i*.

If you are not satisfied with SPMs suggestions for error covariances, you can insert your own list of Vi components after design specification, before you estimate the model.

## Verification of covariance specificationsEdit

Covariance components can be verified using SPMs **Review Design** facility - in the Menu there is an item called *Explore Covariance structure*.