pwr (version 1.2-0)

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", "less","greater"))

Arguments

h

Effect size

n1

Number of observations in the first sample

n2

Number of observationsz in the second sample

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 '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

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

See Also

ES.h, pwr.2p.test, power.prop.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="greater")

## 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")