[R] one-way ANOVA model, with one factor, an unbalanced design and unequal variances

Steven stevenworthington at hotmail.com
Thu Apr 21 20:28:06 CEST 2011


i'm looking for an R function to fit a one-way ANOVA with one factor
containing 10 levels. The factor levels have different numbers of
observations (varying between 20 to 40). For most of the dependent variables
i'm testing there are unequal variances among the factor levels.

I see the function oneway.test:

oneway.test(variable ~ factor, data=dataset)

which by default does not assume equal variances. I also see the basic ANOVA
function (aov), which, I think, is OK for unbalanced designs. I get a
different F ratio, however, when using these two functions on the same data,
which seems to indicate that the aov function assumes equal variances.

My question: is there an R function that performs a one-way ANOVA while not
assuming a balanced design *or* equal variances? Does the oneway.test
function, for example, assume a balanced design?



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