Calculate student t-test

t_test.R

# one sample t-test
t_test1 <- function(x.n, x.mu, x.var, mu, side=0)
{
  nu <- x.n - 1
  t <- (x.mu - mu) / sqrt(x.var / x.n)
  p <- p.value(pt, t, params=nu, side=side)
  data.frame(mean=x.mu, df=nu, statistic=t, p.value=p)
}

# two samples t-test
t_test2 <- function(x.n, x.mu, x.var, y.n, y.mu, y.var, var.equal=F, side=0)
{
  mu <- x.mu - y.mu
  if (var.equal) {
    nu <- x.n + y.n - 2
    s <- sqrt(((x.n-1)*x.var + (y.n-1)*y.var) / nu)
    t <- mu / (s * sqrt(1/x.n + 1/y.n))
  }
  else {
    nu <- (x.var/x.n + y.var/y.n)^2 / (x.var^2/x.n^2/(x.n-1) + y.var^2/y.n^2/(y.n-1))
    t <- mu / sqrt(x.var/x.n + y.var/y.n)
  }
  p <- p.value(pt, t, params=nu, side=side)
  data.frame(mean=mu, df=nu, statistic=t, p.value=p)
}