This calculator provides the Peto odds ratio and the observed - expected differences, together with the variance of the observed - expected difference. This allows you to calculate the result of a meta-analysis of different studies. Refer to the Cochrane Collaboration for details. This calculator works off-line. (IE4)

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

		Intervention
		EXPTL group	CTRL group
		(A+C)	(B+D)
OUTCOME	present	A =	B =	total A+B=
	absent	C =	D=	total C+D=

Odds ratio estimate (OR) =
95% confidence interval =
Observed - expected = Variance observed - expected =
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.
This calculation is based on the null hypothesis and provides an estimate of the true odds ratio. Under the null hypothesis that treatment has no effect on outcome, the difference between the observed and the expected would have zero difference and variance. The advantage of this approach over direct calculation is that it will accept zero results without generating infinity. 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@Postmaster.co.uk
24/3/2006
Reference Chalmers et al Effective Care in pregnancy and childbirth. p63