Hi Martin
I used the words "suggest an effect" deliberately because, ROTn-1: if
you plot the "raw" data for a meta-analysis (measure of central tendency
and confidence interval for each included study), you get a visual
impression that suggests the direction of effect. The meta-analysis
quantifies the visual impression of direction and provides a confidence
interval. If the meta-analysis is consistent with the visual impression,
it confirms its face validity. If the meta-analysis is NOT consistent
with your visual impression, you should check the numbers, graphing and
calculations!
Michael
-----Original Message-----
From: Martin Dawes, Dr. [mailto:[log in to unmask]]
Sent: 02 July 2008 18:07
Subject: Re: quesetionable statistics in meta-analysis - ROT
I agree with the consensus that is accumulating in this discussion on
ROT's but wonder if we have evidence for this following statement
ROTn: if the raw data or simple stats do not suggest an effect, then
the effect found by sophisticated statistics is unlikely to be important
in practice.
Pragmatically this sounds reasonable but isn't that what the Cochrane
logo shows us - advanced stats on small studies (plural) give a result
that is meaningful so maybe it should have a proviso - "in single
adequately powered studies if the raw data....."
Martin
Dr Martin Dawes
Chair Family Medicine
McGill University
515 Pine Avenue West, Montreal
Quebec, Canada H2W 1S4
Tel 514 398 7375 x0469
Fax 514 398 4202
|