Sample size for a 2-group mean superiority or noninferiority test

Computes the sample size in each group (assuming equal sample sizes) required to perform a superiority or noninferiority test for the difference in population means with desired power in a 2-group design. For a superiority test, specify the upper limit (h) for the range of practical equivalence and specify an effect size (es) such that es > h. For a noninferiority test, specify the lower limit (-h) for the range of practical equivalence and specify an effect size such that es > -h. Set the variance planning value to the largest value within a plausible range for a conservatively large sample size.

For more details, see Section 2.14 of Bonett (2021, Volume 1)

Usage

size.supinf.mean2(alpha, pow, var, es, h)

Arguments

alpha

alpha level for hypothesis test

pow

desired power

var

planning value of average within-group variance

es

planning value of mean difference

h

upper or lower limit for range of practical equivalence

Value

Returns the required sample size for each group

References

Bonett DG (2021). Statistical Methods for Psychologists https://dgbonett.sites.ucsc.edu/.

Examples

size.supinf.mean2(.05, .80, 225, 9, 4)
#>  Sample size per group
#>                    143

# Should return:
# Sample size per group 
#                   143