Free statistical calculators
Comparison of proportions calculator
MedCalc uses the "N-1" Chi-squared test as recommended by Campbell (2007) and Richardson (2011).
The confidence interval is calculated according to the recommended method given by Altman et al. (2000).
- Altman DG, Machin D, Bryant TN, Gardner MJ (Eds) (2000) Statistics with confidence, 2nd ed. BMJ Books. (p. 49)
- Campbell I (2007) Chi-squared and Fisher-Irwin tests of two-by-two tables with small sample recommendations. Statistics in Medicine 26:3661-3675.
- Richardson JTE (2011) The analysis of 2 x 2 contingency tables - Yet again. Statistics in Medicine 30:890.
Statistics with Confidence: Confidence Intervals and Statistical Guidelines
Altman DG, Machin D, Bryant TN, Gardner MJ (Eds)
This introduction to confidence intervals has been updated and expanded to include methods for using confidence intervals, with illustrative worked examples and extensive guidelines and checklists to help the novice. There are six new chapters on areas such as diagnostic studies and meta-analyses.