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I'm trying to calculate a power analysis (using pwr package in R) for an unbalanced one-way ANOVA. I'm unsure how to appropriately weight the means or account for the unbalanced design. I currently have: 

groups = 4

n = n for each group (here, n1=12 for group 1, n2=8 for group 2, n3=9, for group 3, and n4=12)

between.var and within.var are known from the ANOVA analysis: 

(between.var=0.004363, within.var=0.003680)

And finally

means = (0.1513, 0.1767, 0.1676, 0.1968).

Any help would be appreciated.

Eray Balkanli
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  • I'm voting to close this question as off-topic because it is about statistics, not programming, and is therefore off-topic. – divibisan Jan 18 '19 at 15:30

1 Answers1

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Working with weighted means is described here: https://www.r-bloggers.com/r-tutorial-series-two-way-anova-with-unequal-sample-sizes/

#read the dataset into an R variable using the read.csv(file) function

dataTwoWayUnequalSample <- read.csv(“dataset_ANOVA_TwoWayUnequalSample.csv”)

#display the data

dataTwoWayUnequalSample

The data looks as the following:

The data in the example

The code for the weighted means:

#use anova(object) to execute the Type I SS ANOVAs

#environment ANOVA

anova(lm(math ~ environment * instruction, dataTwoWayUnequalSample))

#instruction ANOVA

anova(lm(math ~ instruction * environment, dataTwoWayUnequalSample))

The output of the code, taken from the web-page

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