__Calculator for
confidence intervals of odds ratio in an unmatched case control study. For
example groups of cases and controls studied to assess a treatment or exposure
to a suspected causal factor.__ This
calculator works off-line. (IE4)

#### Programme written by DJR Hutchon. Enter data into
the boxes "A","B","C",and "D" or

into boxes "A", "A+B", "C", and "C+D"
Enter titles into blank boxes. Clear all values between entering new sets of
values using the clear button.

#### You can experiment with the effect of different
values keeping the same totals within each study group. The calculator will
adjust the values to keep the totals unchanged.

**This calculator is
for educational use. It is believed accurate but no responsibility for accuracy
of the results is accepted by the author. David J R Hutchon BSc, MB, ChB, FRCOG
Consultant Gynaecologist, Memorial Hospital, Darlington, England.**

You are welcome to keep this page and use the calculator off-line. I would
appreciate an E-mail if you find it useful enough to do so. E-mail to me at DJRHutchon@hotmail.co.uk

31/3/2001

Reference J Martin Bland and Douglas G Altman Statistics Notes: The odds ratio
BMJ 2000;320:1468

This calculator will not calculate correctly with zero in any of the boxes. A different approach is required in these circumstances. One method is to estimate the odds ratio using the null hypothesis.

Odds ratio calculator using null hypothesis approach