size.equiv.prop2 {statpsych}

Sample size for a 2-group proportion equivalence test

Description

Computes the sample size in each group (assuming equal sample sizes) required to perform an equivalence test for the difference in population proportions with desired power in a 2-group design. The value of h specifies a range of practical equivalence, -h to h, for the difference in population proportions. The absolute difference in the proportion planning values must be less than h. Equivalence tests often require a very large sample size. Equivalence tests usually use 2 x alpha rather than alpha (e.g., use alpha = .10 rather than alpha = .05).

Usage

size.equiv.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

upper limit for range of practical equivalence

Value

Returns the required sample size for each group

Examples

size.equiv.prop2(.1, .8, .30, .35, .15)

# Should return:
# Sample size per group
#                   288