Revised: 07/23/2013 -- added NNM -- the Number Needed to
Mis-diagnose (thanks to Farrokh Habibzadeh)

This page computes various statistics from a 2-by-2 table. It will calculate the Yates-corrected chi-square, the Mantel-Haenszel chi-square, the Fisher Exact Test, and other indices relevant to various special kinds of 2-by-2 tables:

- analysis of risk factors for unfavorable outcomes (odds ratio, relative risk, difference in proportions, absolute and relative reduction in risk, number needed to treat)
- analysis of the effectiveness of a diagnostic criterion for some condition (sensitivity, specificity, pos & neg predictive values, pos & neg likelihood ratios, diagnostic and error odds ratios)
- measures of inter-rater reliability (% correct or consistent, mis-classification rate, kappa, Forbes' NMI)
- other measures of association (contingency coefficient, Cramer's phi coefficient, Yule's Q)

Many of these concepts are explained in detail in an online
Evidence-based
Medicine
Glossary. For more information about a particular index,
click on
the
<__more info__>
link for that index.

**Confidence intervals** for the estimated
parameters are
computed by
a general method (based on "constant chi-square boundaries") given in:
*Statistical Methods for Rates and Proportions* (2^{nd}
Ed.)
Section 5.6, by Joseph L. Fleiss (Pub: John Wiley &
Sons, New
York,
1981). This method is also described in Numerical Recipes in C (2nd
Ed.)
Section 15.6, by William H. Press et al. (Pub: Cambridge University
Press,
Cambridge UK, 1992)

Enter numbers into the four cells below. Make sure that the row and column totals add up correctly. Then click the Compute button.

**Warning: Do not enter
cell counts with a
leading zero!
**That is, if a cell count is 34, enter it as 34, **not
as 034**.
Some browsers will mis-interpret some numbers entered with
leading
zeros, and will produce **wrong results** (with no
warning
message). For
more information about this, and for other things to be aware of before
using
this page for the first time, make sure you read the
JavaStat user interface guidelines.

**Observed
Contingency Table**