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

Source: R/statpsych1.R

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.

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 for each group

Examples

size.test.mean2(.05, .95, 100, 10, 1) 
#>  n1 n2
#>  27 27

# Should return:
# n1  n2
# 27  27