Interaction analyses — How large a sample do I need? (part 3)

pwr.r.test(r=0.25,sig.level = 0.05,power = 0.8)
approximate correlation power calculation (arctangh transformation)
n = 122.4466
r = 0.25
sig.level = 0.05
power = 0.8
alternative = two.sided
(log(2)+1)*.25
[1] 0.4232868
pwr.r.test(r=0.125,sig.level = 0.05,power = 0.8)
approximate correlation power calculation (arctangh transformation)
n = 499.1926
r = 0.125
sig.level = 0.05
power = 0.8
alternative = two.sided

What about all those published interactions with small samples?

So how large a sample do I need?

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PhD in Neuroscience, Postdoc at U Pittsburgh. https://twitter.com/david_baranger

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David Baranger

David Baranger

PhD in Neuroscience, Postdoc at U Pittsburgh. https://twitter.com/david_baranger

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