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Re: st: stata resources available for funnel plots?


From   Neil Shephard <nshephard@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: stata resources available for funnel plots?
Date   Thu, 5 Mar 2009 11:50:04 +0000

On Thu, Mar 5, 2009 at 11:30 AM, Rosa Gini
<rosa.gini@arsanita.toscana.it> wrote:
> dear statalisters,
>
> we are developing a project for comparison of institutional performance,
> and wish to perform the analysis suggested by david spiegelhalter in his
> papers
>
> D Spiegelhalter, Funnel plots for institutional comparison,  Qual Saf
> Health Care 2002;11:390-391
>
> http://qshc.bmj.com/cgi/content/extract/11/4/390-a
>
> David J. Spiegelhalter, Funnel plots for comparing institutional
> performance, Statistics in Medicine, Volume 24 Issue 8, Pages 1185 - 1202
>
> http://www3.interscience.wiley.com/journal/109800995/abstract?CRETRY=1&SRETRY=0
>
> in short, the idea is to plot proportions (or standardized rates,...) in
> funnel plots against a measure of their precision in order to detect
> outliers. there are available resources to perform such analysis with MS
> Excel on some NHS websites such as
>
> http://www.erpho.org.uk/topics/tools/funnel.aspx#17487
>
>
>
> we are looking for available resources in Stata, but we only found "funnel"
> which is meant to interact with metan which is written for more complex
> comparisons (ie metanalysis of risk ratio, odds ratios, risk differences)
>
> any suggestion? should we try and adapt metan?
>

Very interesting, I've been meaning to write some code to do this, but
have been exceptionally busy on other projects which have taken
priority.

Reading the papers, I think the use of proportions (and changes
thereof), standardised rates, and continuous responses is fairly
straight-forward and using -metan-/-funnel- is justifiable.  What
-meatn-/-funnel- don't currently do at the moment though is account
for over-dispersion which is common in comparing institutions.  This
seems to basically be done by scaling (or inflating as used on pp1194
of the second reference) the variance by a factor to widen the funnel
which seems quite straight-forward really, so I _think_ you'd probably
be able to adapt -funnel- to have an option to allow for
over-dispersion and this option should probably allow for both
additive and multiplicative over-dispersion.

I'd be very interested to know how things develop and more than happy
to help test code.

Regards

Neil

-- 
"The combination of some data and an aching desire for an answer does
not ensure that a reasonable answer can be extracted from a given body
of data." ~ John Tukey

Email - nshephard@gmail.com
Website - http://slack.ser.man.ac.uk/
Photos - http://www.flickr.com/photos/slackline/

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