Thomas Souers wrote:
>
> Hello, I have two questions regarding multiple comparison tests for a one-way ANOVA
>(fixed effects model).
>
> 1) Consider the "Protected LSD test," where we first use the F statistic to test the
>hypothesis of equality of factor level means. Here we have a type I error rate of
>alpha. If the global F test is significant, we then perform a series of t-tests
>(pairwise comparisons of factor level means), each at a type I error rate of alpha.
>This may seem like a stupid question, but how does this test preserve a type I error
>for the entire experiment?
As you (nearly) say, "[Only i]f the global F test is significant, we
then perform a series of t-tests "
>
> 2) Secondly, are contrasts used primarily as planned comparisons? If so, why?
It depends on the research question.
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