Sample size for a 2-group Pearson correlation difference confidence interval

Computes the sample size required to estimate a difference in population Pearson or partial correlations with desired confidence interval precision in a 2-group design. Set the correlation planning values to the smallest absolute values within their plausible ranges for a conservatively large sample size.

size.ci.cor2(alpha, cor1, cor2, w)

Arguments

alpha

alpha level for 1-alpha confidence

cor1

group 1 correlation planning value

cor2

group 2 correlation planning value

w

desired confidence interval width

Value

Returns the required sample size

References

Bonett DG, Wright TA (2000). “Sample size requirements for estimating Pearson, Kendall and Spearman correlations.” Psychometrika, 65(1), 23--28. ISSN 0033-3123, doi:10.1007/BF02294183 .

Examples

size.ci.cor2(.05, .8, .5, .2)
#>  Sample size per group
#>                    271

# Should return:
# Sample size per group
#                   271