| power.t.test {ctest} | R Documentation |
Power calculations for one and two sample t tests
Description
Compute power of test, or determine parameters to obtain target power.
Usage
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"))
Arguments
n |
Number of observations (per group) |
delta |
True difference in means |
sd |
Standard deviation |
sig.level |
Significance level (Type I error probability) |
power |
Power of test (1 minus Type II error probability) |
type |
Type of t test |
alternative |
One- or two-sided test |
Details
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
compute them.
Value
Object of class "power.htest", a list of the arguments
(including the computed one) augmented with method and
note elements.
Note
uniroot is used to solve power equation for unknowns, so
you may see errors from it, notably about inability to bracket the
root when invalid arguments are given.