pwr.t2n.test: Power calculations for two samples (different sizes) t-tests...

In pwr: Basic Functions for Power Analysis

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"

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.

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.

Author(s)

Stephane Champely <[e-mail]> but this is a mere copy of Peter Dalgaard work (power.t.test)

References

Cohen, J. (1988). Statistical power analysis for the behavioral sciences (2nd ed.). Hillsdale,NJ: Lawrence Erlbaum.

Examples

## Exercise 2.3 p. 437 from Cohen (1988)
pwr.t2n.test(d=0.6,n1=90,n2=60,alternative="greater")

pwr documentation built on March 17, 2020, 5:11 p.m.