power.anova.test {stats} | R Documentation |
Compute power of test or determine parameters to obtain target power.
power.anova.test(groups = NULL, n = NULL, between.var = NULL, within.var = NULL, sig.level = 0.05, power = NULL)
groups |
Number of groups |
n |
Number of observations (per group) |
between.var |
Between group variance |
within.var |
Within group variance |
sig.level |
Significance level (Type I error probability) |
power |
Power of test (1 minus Type II error probability) |
Exactly one of the parameters groups
, n
, between.var
,
power
, within.var
, and sig.level
must be passed as NULL,
and that parameter is determined from the others. Notice that
sig.level
has non-NULL default so NULL must be explicitly
passed if you want it computed.
Object of class "power.htest"
, a list of the arguments
(including the computed one) augmented with method
and
note
elements.
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.
Claus EkstrĂ¸m
power.anova.test(groups = 4, n = 5, between.var = 1, within.var = 3) # Power = 0.3535594 power.anova.test(groups = 4, between.var = 1, within.var = 3, power = .80) # n = 11.92613 ## Assume we have prior knowledge of the group means: groupmeans <- c(120, 130, 140, 150) power.anova.test(groups = length(groupmeans), between.var = var(groupmeans), within.var = 500, power = .90) # n = 15.18834