2 x 2 between-subjects Anova power analysis

2x2-anova-power-analysis.R

library(ggplot2)
library(purrr)
library(pwr2)

power_analysis_go_brrr <- function(f, n) {
  res <- pwr.2way(a = 2, b = 2, f.A = f, f.B = f, alpha = .05, size.A = n/2, size.B = n/2)
  data.frame(f = f, 
             n = n, 
             power_a = res$power.A,
             power_b = res$power.B,
             power_ab = res$power)
}

combinations <- expand.grid(f = c(.10, .15, .20, .25, .30), 
                            n = seq.int(2, 1000, by=50))

lots_of_numbers <- pmap_dfr(combinations, power_analysis_go_brrr)

lots_of_numbers |> 
  ggplot(aes(n, power_a, color=as.factor(f), shape=as.factor(f))) + 
  geom_point() +
  geom_line() +
  scale_x_continuous(breaks = seq.int(0, 1e7, by=100)) +
  scale_y_continuous(breaks = seq.int(.10, 1, by=.1)) +
  labs(x = "Total sampelstorlek",
       y = "Power",
       color = "Cohen's f",
       shape = "Cohen's f",
       title = "2 x 2 between-subjects Anova",
       subtitle = "alpha = 0.05, samma varians, endast huvudeffekter")