Calculator for confidence intervals of relative risk This calculator works off-line. (IE4)

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

		Group characteristic
		Treatment	Control
		(A+C)	(B+D)
OUTCOME	Total "better" A+B=	A =	B =
	Total "no better" C+D	C =	D=

Relative risk R =
95% confidence interval = or treatment is
A permanent record of the analysis can be obtained by printing the page.
Ref: Gardner M J and Altman D G. Statisitics with confidence. BMJ publications. Reprint 1994 p 51-52
Relative risk = (A/{A+C})/(B/{B+D})
Standard Error oflog Relative risk(SElogR) =sqrt((1/A)-(1/(A+C))+(1/B)-(1/(B+D)))
lower limit= the exponential of (log(Rel risk)-(1.96*SElogR))
upper limit= the exponential of (log(Rel risk)+(1.96*SElogR))

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
1/10/1999

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Last modified: 01/08/2010 16:46:34