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4.5 Transformations 61variance) will be correlated. The Levene and Shapiro-Wilk tests assume that the residualsare independent Normally-distributed observations. Their test probabilities may thereforebe too low and generate too many significant results. So the use of a smaller criticalprobability value provides some protection against spurious messages.As expected, GenStat reports evidence of both non-homogeneity of the residualvariance, and of non-Normality.Message: evidence of non-homogeneity of residual variance for Type andHaul.Message: the Shapiro-Wilk test shows evidence of non-Normality.The ANOVA Options menu does notprint the tests themselves, but theseare given if you use the Assumptiontests box ANOVA Further Outputmenu (Figure 4.16). The setting inthe options menu is intended toallow unobtrusive backgroundtesting, while that in the furtheroutput menu gives further output as requested.Figure 4.16Tests of assumptions for ANOVAVariate: NumberLevene tests for homogeneity of varianceAnalysis of varianceVariate: Absolute residualsSource of variation d.f. s.s. m.s. v.r. F pr.Haul stratum 11 13.8440 1.2585 7.17Haul.*Units* stratumType 3 6.0333 2.0111 11.45