Bootstrap confidence interval for difference in means with paired data

bootstrap_means_paired.R

# function

mbPaired <- function(x, y, B = 1000) {
  lx <- length(x)
  ly <- length(y)
  if (lx != ly) stop('x and y differ in length')
  # sample indices
  M <- sample(seq_len(lx), size = lx * B, replace = T)
  # calculate differences and mean of differences
  diffs <- x[M] - y[M]
  diffs <- matrix(diffs, ncol = B)
  diffs <- colMeans(diffs)
  #results
  c(mean(x) - mean(y), quantile(diffs, c(0.025, 0.975)))
}

# example

x <- exp(seq(0, 5, length.out = 100))
y <- log(1:100) ^ 2
mbPaired(x, y)