pwr (version 1.0)

pwr.2p2n.test: Power calculation for two proportions (different sample sizes)

Description

Compute power of test, or determine parameters to obtain target power.

Usage

pwr.2p2n.test(h = NULL, n1 = NULL, n2 = NULL, sig.level = 0.05, power = NULL, alternative = c("two.sided", "one.sided"))

Arguments

h

Effect size

n1

Number of observations in the first sample

n2

Number of observations in the second sample

sig.level

Significance level (Type I error probability)

power

Power of test (1 minus Type II error probability)

alternative

One- or two-sided test

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 'h','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

J. Cohen (1988) Statistical power analysis for the behavioral scientist. Lawrence Erlbaum Associates, publishers.

See Also

pwr.2p.test

Examples

## Exercise 6.3 p. 200 from Cohen (1988)
pwr.2p2n.test(h=0.30,n1=80,n2=245,sig.level=0.05,alternative="one.sided")

## Exercise 6.7 p. 207 from Cohen (1988)
pwr.2p2n.test(h=0.20,n1=1600,power=0.9,sig.level=0.01,alternative="two.sided")