size.supinf.prop2 {statpsych}

Sample size for a 2-group superiority or inferiority test of proportions

Description

Computes the sample size in each group (assuming equal sample sizes) required to perform a superiority or inferiority test for the difference in population proportions with desired power in a 2-group design. For a superiority test, specify the upper limit (h) for the range of practical equivalence and specify values of p1 and p2 such that p1 - p2 > h. For an inferiority test, specify the lower limit (-h) for the range of practical equivalence and specify values of p1 and p2 such that p1 - p2 > -h. This function sets the effect size equal to p1 - p2.

Usage

size.supinf.prop2(alpha, pow, p1, p2, h)

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

h

lower or upper limit for range of practical equivalence

Value

Returns the required sample size for each group

Examples

size.supinf.prop2(.05, .9, .35, .20, .05)

# Should return:
# Sample size per group
#                   408