Find sample size:

If you know the correlation coefficient, use this form to find how many subjects you need.
Find correlation coefficient:

If you know the number of subjects, use this form to find smallest detectable correlation.
Correlation coefficient (rho):
Click here for sample size:
You will need subjects
Number of subjects:
Click here for rho:

You can detect r >
or r <
For different power or significance level, change the fields below:
Alpha: Prob(reject H0 when H0 is true)
Power: Prob(reject H0 when H1 is true)
Choose another study design
v. 03/03
Source: G.W. Snedecor & W.G. Cochran
Statistical Methods (7th ed., p. 104)