size.test.prop2: Sample size for a test of a 2-group proportion difference

In statpsych: Statistical Methods for Psychologists

Sample size for a test of a 2-group proportion difference

Description

Computes the sample size in each group required to test a difference in population proportions with desired power (using a continuity correction) in a 2-group design. This function requires planning values for both proportions. Set each proportion planning value to .5 for a conservatively large sample size requirement. This function does not require the planning value for the proportion difference (effect size) to equal the difference of the two proportion planning values; for example, the planning value of the proportion difference could be set equal to a minimally interesting effect size.

For more details, see Section 2.23 of Bonett (2021, Volume 3)

Usage

size.test.prop2(alpha, pow, p1, p2, es)

Arguments

alpha	alpha level for hypothesis test
pow	desired power
p1	planning value of proportion for group 1
p2	planning value of proportion for group 2
es	planning value of proportion difference (effect size)

Value

Returns the required sample size for each group

References

\insertRef

Bonett2021statpsych

Examples

size.test.prop2(.05, .8, .6, .4, .2)
# Should return:
# Sample size per group
#                   106

size.test.prop2(.05, .8, .5, .5, .2)
# Should return:
# Sample size per group
#                   109

statpsych documentation built on Jan. 13, 2026, 1:07 a.m.