power.prop2 {statpsych}

Approximates the power of a two-sample proportion test for planned sample sizes

Description

Computes the approximate power for a test of equal population proportions in a 2-group design for the planned sample sizes. This function requires planning values for both proportions. Set the proportion planning values to .5 for a conservatively low power estimate. The planning value for the proportion difference could be set to the difference of the two proportion planning values or it could be set to a minimally interesting effect size.

Usage

power.prop2(alpha, n1, n2, p1, p2, es)

Arguments

alpha

alpha level for hypothesis test

n1

planned sample size for group 1

n2

planned sample size for group 2

p1

planning value of proportion for group 1

p2

planning value of proportion for group 2

es

planning value of proportion difference

Value

Returns the approximate power of the test

Examples

power.prop2(.05, 60, 40, .5, .5, .2)

# Should return:
#     Power
# 0.4998515