One-sample chi-square
Find sample size: If you know the proportion, use this form to find how many subjects you need. [Enter decimals, not percentages: 0.25 for 25%]	Find effect size: If you know the number of subjects, use this form to find largest and smallest detectable proportions. [Enter decimal, not percentage: 0.25 for 25%]
Group proportion: Comparison proportion: Click here for sample size: You will need subjects	Number of subjects: Comparison proportion: Click here for effect size: You can detect p < You can detect p >
For different power or significance level, change the fields below: Alpha: Prob(reject H0 when H0 is true) 0.05 0.01 0.005 0.001 0.0005 0.0001 Power: Prob(reject H0 when H1 is true) 0.80 0.90
Choose another study design v. 03/03 Contact: sfh2@columbia.edu Source: J.L. Fleiss, et al. Statistical Methods for Rates & Proportions (3rd ed., p. 30)