A simulation incrementing sample size until p < 0.05

inc_sample_size.R

library(purrr)

sim_inc_sample <- function(N_start = 20, N_end = 100,
                           mu = 0, sigma = 1, sig = 0.05) {
  not_sig <- TRUE
  N <- N_start
  x1 <- rnorm(N_end, mu, sigma)
  x2 <- rnorm(N_end, mu, sigma)
  while(not_sig & N <= N_end) {
    p_value <- t.test(x1[1:N], x2[1:N])$p.value
    if (p_value < sig) {
      not_sig <- FALSE
    } else {
      N <- N + 1
    }
  }
  return(N)
}

set.seed(20180324)
R <- 1000
N_start <- 20
N_end <- 100
n <- purrr::map_dbl(seq_len(R), ~ sim_inc_sample(N_start, N_end))
sum(n == N_start) / R
sum(n <= N_end) / R