Chi-square test | |
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Find sample size: If you know the two proportions, use this form to find how many subjects you need. |
Find effect size: If you know the proportion for group 1 and the number of subjects, use this form to find largest and smallest detectable proportions for group 2. |

The calculations here use equations 4.18 & 4.19 in J.L. Fleiss, et al.,
Statistical Methods for Rates and Proportions, 4th ed., and are consistent with their Table A.4. The results here may differ from other webpages or software because most of them ignore the
continuity correction. The Fleiss book discusses the importance of the continuity correction;
see also Levin and Chen, American Statistician 53:62-66. Choose another study design v. 03/03 Contact: sfh2@columbia.edu |