size.test.prop2 {statpsych} | R Documentation |
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.
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
Examples
size.test.prop2(.05, .8, .5, .5, .2)
# Should return:
# Sample size per group
# 109
size.test.prop2(.05, .8, .3, .1, .2)
# Should return:
# Sample size per group
# 71