[R] power analyses for mixed effects lmer models

[LeeDetroit]

Hi all,

I'm new (post #1!) and I hope you'll forgive me if I'm acting like an
idiot...

I have been asked for some power analyses for some mixed-effects models I'm
running using lmer. My studies nearly always contain mixes of
repeated-measures and between-subjects predictor variables.

As an example, suppose I want to see if men or women show a stronger word
frequency effect. I have 50 words of varying frequency that I show to 30 men
and 30 women, who are supposed to decide as quickly as possible whether it's
a real word. So my data object would end up being 3000 lines long, and look
like this:

Subject  Word  Sex  Frequency  ReactionTime
s1 w1 M 23 2543
s1 w2 M 67 1438
s1 w3 M 1 8033
...
s60 w50 F 4 1099

I analyze this with 

lmer(log(ReactionTime) ~ (Sex * Frequency) + (1|Subject) + (1|Word)

Does anyone know how I might do power analyses or compute effect sizes in
this kind of situation?

Thanks.

--Lee
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