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This page will give some tips on aspects of looking at residuals in order to assess non-normality. In particular it will stress how in repeated measures data, the thing that matters is the distributions of differences between pairs of measures (or more general contrasts in the repeated measures). in grouped data, it is the residuals adjusted for group means that matter Consider this very small example: X1 X2 1 2 2 1 3 2 1001 1002 The distributions of the variables are very skewed. The distribution of the differences (for a repeated measures t-test) are at least symmetrical, if not normal. [Last updated on 21 September, 2010] Return to Statistics FAQ page Return to Statistics main page Return to CBU main page These pages are maintained by Ian Nimmo-Smith and Peter Watson