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st: RE: Risk differences in Epitab
I personally compute confidence intervals for risk differences using the
-somersd- package, downloadable from SSC. If Y is a binary outcome
variable and X is a binary exposure variable, then the command
somersd X Y, tr(z)
gives a confidence interval for the difference in risk between exposed
and unexposed individuals, using the hyperbolic arctangent (Fisher's
z-transform) as a Normalizing and variance-stabilizing transformation.
You can also use the option -tr(asin)- to use the arcsine
transformation.
Hope this helps.
Roger
Roger Newson
Lecturer in Medical Statistics
POSTAL ADDRESS:
Respiratory Epidemiology and Public Health Group
National Heart and Lung Institute at Imperial College London
St Mary's Campus
Norfolk Place
London W2 1PG
STREET ADDRESS:
Respiratory Epidemiology and Public Health Group
National Heart and Lung Institute at Imperial College London
47 Praed Street
Paddington
London W1 1NR
TELEPHONE: (+44) 020 7594 0939
FAX: (+44) 020 7594 0942
EMAIL: [email protected]
WEBSITE: http://www.kcl-phs.org.uk/rogernewson/
Opinions expressed are those of the author, not of the institution.
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Edward Norton
Sent: 09 February 2006 04:02
To: [email protected]
Subject: st: Risk differences in Epitab
Statalist,
I would like to compute a risk difference, instead of the default
risk ratio, using the -cs- command in epitab. However, when I try to
run commands like
gen ones = 1
cs y x, by(a b c) standard(ones) rd
Stata 9.0 returns a error of "invalid sytax" number 198. The same
command without "rd" (meaning the default risk ratio) works fine.
Any suggestions about how to compute risk differences would be
appreciated.
Edward
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