This EXCEL [[attachment:fishr.xls|spreadsheet]] computes power comparing two group correlations using [[FAQ/WilliamsSPSS/Fisher|Fisher's transform]] given the two group correlations and their sample sizes. This calculation may also be done [[FAQ/fishrpow| in R.]]

The same results may also be obtained from [[http://www.quantitativeskills.com/sisa/statistics/correl.htm|this power calculator]] although this calculator assumes the second correlation comes from a population, rather than a sample. In practice this means the second sample is thought of as having an arbitrarily large value e.g. 10000.