[EpiData-list] EpiData statistics documentation.

epidata-list at lists.umanitoba.ca epidata-list at lists.umanitoba.ca
Mon May 30 09:30:02 CDT 2011


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


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