size.test.mean2: Sample size for a test of a 2-group mean difference

In statpsych: Statistical Methods for Psychologists

Sample size for a test of a 2-group mean difference

Description

Computes the sample size in each group required to test a difference in population means with desired power in a 2-group design. Set R =1 for equal sample sizes. Set the variance planning value to the largest value within a plausible range for a conservatively large sample size.

Usage

size.test.mean2(alpha, pow, var, es, R)

Arguments

alpha	alpha level for hypothesis test
pow	desired power
var	planning value of average within-group variance
es	planning value of mean difference
R	n2/n1 ratio

Value

Returns the required sample size per group

Examples

size.test.mean2(.05, .95, 100, 10, 1) 

# Should return:
#      n1  n2
# [1,] 27  27
 

statpsych documentation built on July 9, 2023, 6:50 p.m.