simple_power_analysis.R

library(tidyverse)

probs <- c(.6, .8)
df <- expand_grid(subid = 1:10, 
                  condition = 1:2, 
                  trial_num = 1:12) %>%
  group_by(condition) %>%
  mutate(correct = rbinom(n = n(), size = 1, prob = probs[condition][1]))


ms <- df %>%
  group_by(subid, condition) %>%
  summarise(mean_correct = mean(correct))

ggplot(ms, 
       aes(x = condition, y = mean_correct, col = condition)) + 
  geom_jitter(width = .1, height = 0) + 
  geom_hline(yintercept = .5, lty = 2)

iu_mean <- mean(ms$mean_correct[ms$condition == 1])
ip_mean <- mean(ms$mean_correct[ms$condition == 2])
pooled_sd <- sd(ms$mean_correct)
d <- (ip_mean - iu_mean) / pooled_sd


pwr::pwr.t.test(d = d, sig.level = .05, power = .8, 
                type = "two.sample", alternative = "two.sided")