[R] sample size specification in pwr2::pwr.2way

[Floris van Vugt]

Dear R Help list,

My question is how sample size is specified in 2-way ANOVA power calculation in the pwr2 package.

In the function pwr2::pwr.2way documentation it gives an example use (source https://rdrr.io/cran/pwr2/man/pwr.2way.html) :
```
## Example 1
pwr.2way(a=3, b=3, alpha=0.05, size.A=4, size.B=5, f.A=0.8, f.B=0.4)
```

I have trouble understanding what the total sample size is in this case. The documentation says `a` refers to the number of groups in Factor A, and `size.A` is the sample size per group in Factor A. Similarly for Factor B.

Based on that, I inferred that Factor A is supposed to have 3 groups with 4 individuals per group, meaning a total of 12 individuals in the experiment as a whole. However, in Factor B there are 3 groups with 5 individuals per group, which would lead to a total of 15 individuals. So my conclusions are contradictory: are there 12 or 15 individuals in this experimental design? Or yet a different number?

Any help appreciated.

Best wishes
Floris


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