I am trying to perform a levenetest on my two-way anova.

`leveneTest(Score ~ Party + Group, data = Data) `

But R just screams at me saying

`Error in leveneTest.formula(formula(y), data = model.frame(y), ...) : Model must be completely crossed formula only. `

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#### Best Answer

I think you are getting an error as your model does not include an interaction term. I would try first creating a model fit using the `lm`

function:

`fit <- lm(Score ~ Party + Group, data = Data) `

and then using the `levene.test`

function in the `s20x`

package as it is a little less finicky.

`levene.test(fit) `

In saying all that, levene tests are actually a really poor way of checking equality of variance (EoV). They are overly sensitive to deviations, while ANOVAs are actually quite robust. You are better off just looking at a plot (i.e. `plot(fit, which =1)`

) and visually assessing it for EoV. If it is for an assignment that requires it, then ignore the latter advice. Also, the samething goes for normality and the shapiro-wilks test….

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