Computes the sample size in each group required to test a difference in
population means with desired power in a 2-group design. Set the variance
planning value to the largest value within a plausible range for a
conservatively large sample size. Set R =1 for equal sample sizes.
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 for each group
Examples
size.test.mean2(.05, .95, 100, 10, 1)
#> n1 n2
#> 27 27
# Should return:
# n1 n2
# 27 27
size.test.mean2(.05, .95, 100, 10, 3)
#> n1 n2
#> 19 57
# Should return:
# n1 n2
# 19 57
size.test.mean2(.05, .95, 100, 10, .5)
#> n1 n2
#> 40 20
# Should return:
# n1 n2
# 40 20