Sample size for a paired-samples standardized mean difference confidence interval

Computes the sample size required to estimate two types of population standardized mean differences (unweighted standardizer and single group standardizer) with desired confidence interval precision in a paired-samples design. Set the standardized mean difference planning value to the largest value within a plausible range, and set the Pearson correlation planning value to the smallest value within a plausible range for a conservatively large sample size.

Usage

size.ci.stdmean.ps(alpha, d, cor, w)

Arguments

alpha

alpha level for 1-alpha confidence

d

planning value of standardized mean difference

cor

planning value of correlation between measurements

w

desired confidence interval width

Value

Returns the required sample size for each standardizer

References

Bonett DG (2009). “Estimating standardized linear contrasts of means with desired precision.” Psychological Methods, 14(1), 1–5. ISSN 1939-1463, doi:10.1037/a0014270 .

Examples

size.ci.stdmean.ps(.05, 1, .65, .6)
#>                            Sample size
#> Unweighted standardizer:            46
#> Single group standardizer:          52

# Should return:
#                            Sample Size
# Unweighted standardizer:            46
# Single group standardizer:          52