-----Original Message-----
From: A UK-based worldwide e-mail broadcast system mailing list
[mailto:[log in to unmask]]On Behalf Of Chumun, Chris (MBWAR st)
Sent: 06 July 2005 15:17
To: [log in to unmask]
Subject: Significance testing query - pre/post studies with test/control
s amples
Hello all
I'm looking at pre and post studies. Both studies have a test and control
sample. Each of the four cells contain 400 respondents and every respondent
is a different person.
We are looking at comparing percentage scores. For example:
Test Control
Pre 50 55
Post 52 59
The difference between control and test for pre is 5 percentage points.
The difference between control and test for post is 7 percentage points.
Therefore the difference between post and pre is +2 percentage points.
We want to test if this "+2" is significant.
Can anybody help?
Kind regards
Chris
Chris Chumun
Statistics Executive
Millward Brown
Olympus Avenue, Tachbrook Park, Warwick, CV34 6RJ
t: +44 (0) 1926 826335
f: +44 (0) 1926 833600
www.millwardbrown.com
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