pwr.t2n.test: Power calculations for two samples (different sizes) t-tests of means
Description
Compute power of tests or determine parameters to obtain target
power (similar to as power.t.test).
Usage
pwr.t2n.test(n1 = NULL, n2= NULL, d = NULL, sig.level = 0.05, power = NULL, alternative = c("two.sided", "less","greater"))
Arguments
n1
Number of observations in the first sample
n2
Number of observations in the second sample
d
Effect size
sig.level
Significance level (Type I error probability)
power
Power of test (1 minus Type II error probability)
alternative
a character string specifying the alternative hypothesis,
must be one of "two.sided" (default), "greater" or
"less"
Value
Object of class '"power.htest"', a list of the arguments
(including the computed one) augmented with 'method' and 'note'
elements.
Details
Exactly one of the parameters 'd','n1','n2','power' and
'sig.level' must be passed as NULL, and that parameter is
determined from the others. Notice that the last one has non-NULL
default so NULL must be explicitly passed if you want to compute
it.
References
Cohen, J. (1988). Statistical power analysis for the
behavioral sciences (2nd ed.). Hillsdale,NJ: Lawrence Erlbaum.