This EXCEL [[attachment:fishr.xls|spreadsheet]] computes a single group sample size when comparing two group correlations using [[FAQ/WilliamsSPSS/Fisher|Fisher's transform]] given the two group correlations, power of test and the sample size of the other group.

The same results may also be obtained from [[http://www.quantitativeskills.com/sisa/statistics/correl.htm|this power calculator]] although this calculator only compares equal sized groups.