[EpiData-list] RE EpiData-list Digest, Vol 91, Issue 9 - EpiData statistics documentation.

epidata-list at lists.umanitoba.ca epidata-list at lists.umanitoba.ca
Mon May 30 12:41:20 CDT 2011


Lu 30 mai 2011

Hello Jamie,

Thank's for your quick answer. You are the spirit of EpiData users.

I'll try to get this reference book.

I would be glad to work with you about this topic and for the cause of 
EpiData. If it may help Jens, it will help us all.

Cordialement,

Réjean Dion, M.D.




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EpiData-list Digest, Vol 91, Issue 9








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Today's Topics:

   1. EpiData statistics documentation.
      (epidata-list at lists.umanitoba.ca)
   2. Re: EpiData statistics documentation.
      (epidata-list at lists.umanitoba.ca)

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Message: 1
Date: Mon, 30 May 2011 10:30:02 -0400
From: epidata-list at lists.umanitoba.ca
Subject: [EpiData-list] EpiData statistics documentation.
To: epidata-list at lists.umanitoba.ca
Message-ID:
 
<OFCEE0BD3B.825D84B0-ON852578A0.004A567F-852578A0.004FA7C8 at isn.rtss.qc.ca>
 
Content-Type: text/plain; charset="ISO-8859-1"

Lu 30 mai 2011

Hello EpiData users,

I'm a new subscriber to this list.

I used recently EpiData Analysis for a matched case-control with a 
controls:case ratio of 38:19 or 2:1 (TAB DISEASE EXPOSURE COMMONID /O /t 
/ex).

In the results output, and in the online help, for the crude table, I 
could'nt find the type of test used, for example, which kind of Chi-square 

(I was able to deduced it was uncorrected), of odds ratio (maximun 
likelihoodestimate [MLE]?) and associated confidence interval (95%?), and 
Fishers exact test (bilateral?). In the adjusted table, the OR [MLE?] is 
provided with a CI (MLE and 95%?), followed by a Chi-square (unspecified 
kind) and another p value (which kind?). The provided p values are rounded 

at 3 digits after the decimal point. The last column provide p-exact 
values (Fishers?), and the one on the adjusted line seems to refer to 
another Chi-squared provided at the bottom of the table. Finally, the 
exact p value for the adjusted results (e.g.: 0.3140) doesn't match with 
the "probability of MLE >= value of MLE of OR (e.g. 6.10) if population OR 

= 1.0" that I obtain (e.g..: 0.00196) with the command MATCH COMMONID 
DISEASE EXPOSURE of Epi Info 6.04d DOS (which is probably equivalent to an 

exact test), and seem discordant with the values of the CI (e.g.: 1.62 to 
34.17).

Using the cohort approach (TAB DISEASE EXPOSURE /RR /t /ex), I found 
similar lack of documentation about statistical tests. 

I would suggest the following to the conceptors of EpiData:
- provide some documentation about statistical tests used in Analysis (do 
any of the users have those answers?);
- provide notes at the bottom of tables to eliminate any ambiguities about 

statistical methods;
- provide p values in the ajusted table with 4 digits after the decimal 
point.

This software work pretty well, but need some ajustments. Keep on the good 

work.

Best regards,

Réjean

Réjean Dion, M.D.
Médecin-conseil en santé publique (maladies infectieuses)
Institut national de santé publique du Québec (INSPQ) /
Laboratoire de santé publique du Québec (LSPQ)
20045, chemin Sainte-Marie,
Sainte-Anne-de-Bellevue (Québec)
Canada H9X 3R5
Tél.: (514) 457-2070 poste 325
Fax.: (514) 457-6346
Courriel / Lotus Notes: rejean.dion at inspq.qc.ca

------------------------------

Message: 2
Date: Mon, 30 May 2011 11:02:37 -0400
From: epidata-list at lists.umanitoba.ca
Subject: Re: [EpiData-list] EpiData statistics documentation.
To: epidata-list at lists.umanitoba.ca
Message-ID: <BLU0-SMTP98AFF72F724FC7BE103867FD7B0 at phx.gbl>
Content-Type: text/plain; charset="iso-8859-1"

Hi Réjean,

The current version uses the statistics recommended in the book 

Statistics with Confidence: Confidence intervals and statistical 
guidelines, 2nd Edition
Douglas Altman (Editor), David Machin (Editor), Trevor Bryant(Editor), 
Stephen Gardner (Editor)
ISBN: 978-0-7279-1375-3
The help file references this book only with respect to Confidence 
Intervals. I agree that, in time, a more complete description of the 
statistical results is warranted. That's something we might want to work 
together on, to give Jens a hand--what do you think?
This version of Analysis does not provide an option to increase the number 
of decimal positions shown with statistics, but more precise results are 
available from results variables such as $exact
The command
result
shows all of the results accessible to the user.
Jamie Hockin

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End of EpiData-list Digest, Vol 91, Issue 9
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