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.
Title of study
(A+C) (B+D)
Study groupsA= B = A+B =
C= D = C+D=

Enter z score for level of confidence required
For 90% enter 1.645, for 95% enter 1.96, for 98% enter 2.236, for 99% enter 2.576
Odds ratio OR =
Confidence interval =
A permanent record of the analysis can be obtained by printing the page.

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