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st: Metan - possible to amend the ado to use difference confidence intervals?


From   "Paul O'Brien" <paul.obrien@afe2.org.uk>
To   statalist <statalist@hsphsun2.harvard.edu>
Subject   st: Metan - possible to amend the ado to use difference confidence intervals?
Date   Wed, 24 Sep 2008 22:33:39 +0100

Having completed the meta-analysis of randomised trials of intrauterine devices, I not want to combine all the individual results in a graph where I input individual pregnancy rates and the standard errors rather than risk difference estimates and their standard errors.

This is _not_ what metan is intended for, but it does what I want well - produces the graphs I am looking for.

however, the confidence intervals calculated by metan gives impossible values at the lower end when applied to individual rates - negative rates.

For the confidence intervals I am using: p ^ exp(+/- 1.96s/(p x ln(p))) as recommended by Kalbfleisch, J.D. and Prentice R.L. (1980). The Statistical Analysis of Failure Time Data. I actually use p x 100 ^ exp(+/- 1.96s/(p x ln(p/100))) as I have the data in percentages.

Would it be possible to change the metan ado to produce these confidence intervals? I also want to produce summary rates, and tests for heterogeneity.

Unfortunately, I have no experience of programming in Stata. I have looked at the metan.ado but cannot see where an amendment might go.

I have lots of graphs of this sort to make with lost of data, so to be able to automate it using metan would make a big difference to me.

Thanks for any help.

Paul


-------------------------------
Dr Paul O'Brien
Raymede Clinic
Westside Contraceptive Services
Westminster Primary Care Trust
Exmoor St
London
W10 6DZ
UK
44 + (0)20 8962 4450






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