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

Source: R/statpsych1.R

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.

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