Message-ID: <20090317104422.B37G4.185896.root@web02-winn.ispmail.private.ntl.com>
Date: 2009-03-17T10:44:22Z
From: si.fu at ntlworld.com
Subject: General help on sample size based on recurrent events
Hello,
I have a general help question that some of you might be able able to help.
I would like to design a study (a two group comparison) based on reduction on events(say hospital admissions). In a previous study hospital admission rate of 140 admissions per 72 patients (over a 4 month period) has been observed. That is rate is about 1.9. In order to see the admission rate reduction of 50% over a 4 month period, i.e. 0.95, in a two group comparison (alpha 0.05) with appropriate power (say 80%) what sort of group sizes are needed.
How would I go about this?
Many Thanks,
Si.