power.mean2 {statpsych}

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

Description

Computes the approximate power of a two-sample t-test for planned sample sizes. For a conservatively low power approximation, set the variance planning values to the largest values within their plausible ranges, and set the effect size to a minimally interesting value. The within-group variances can be unequal across groups and a Satterthwaite degree of freedom adjustment is used to improve the accuracy of the power approximation.

Usage

power.mean2(alpha, n1, n2, var1, var2, es)

Arguments

alpha

alpha level for hypothesis test

n1

planned sample size for group 1

n2

planned sample size for group 2

var1

planning value of within-group variance for group 1

var2

planning value of within-group variance for group 2

es

planning value of mean difference

Value

Returns the approximate power of the test

Examples

power.mean2(.05, 25, 25, 5.0, 6.0, 2)

# Should return:
#     Power
# 0.8398417