power.t.test: Power calculations for one and two sample t tests
Compute the power of the one- or two- sample t test,
or determine parameters to obtain a target power.
power.t.test(n = NULL, delta = NULL, sd = 1, sig.level = 0.05,
power = NULL,
type = c("two.sample", "one.sample", "paired"),
alternative = c("two.sided", "one.sided"),
strict = FALSE, tol = .Machine$double.eps^0.25)
number of observations (per group)
true difference in means
significance level (Type I error probability)
power of test (1 minus Type II error probability)
string specifying the type of t test. Can be abbreviated.
one- or two-sided test. Can be abbreviated.
use strict interpretation in two-sided case
numerical tolerance used in root finding, the default
providing (at least) four significant digits.
Object of class "power.htest", a list of the arguments
(including the computed one) augmented with method and
Exactly one of the parameters n, delta, power,
sd, and sig.level must be passed as NULL, and that
parameter is determined from the others. Notice that the last two have
non-NULL defaults, so NULL must be explicitly passed if you want to
If strict = TRUE is used, the power will include the probability of
rejection in the opposite direction of the true effect, in the two-sided
case. Without this the power will be half the significance level if the
true difference is zero.