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Date:         Thu, 11 Sep 2008 09:49:31 -0400
Reply-To:     "Burleson,Joseph A." <burleson@up.uchc.edu>
Sender:       "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From:         "Burleson,Joseph A." <burleson@up.uchc.edu>
Subject:      Re: paired vs independent samples t-test
Comments: To: humphreyyy1000@yahoo.com
In-Reply-To:  A<96845.10603.qm@web45103.mail.sp1.yahoo.com>
Content-Type: text/plain; charset="iso-8859-1"

No, the paired t-test will always be as or more significant. If the correlation between the pre- and the post-test is exactly r = 0.000, then the two tests will be equal. If the r = 1.000, then the difference scores between the pre- and the post-test will all be identical, meaning that the SD of the difference scores will be zero. In this case, all differences will be infinitely significant.

Joe Burleson

-----Original Message----- From: SPSSX(r) Discussion [mailto:SPSSX-L@LISTSERV.UGA.EDU] On Behalf Of Humphrey Paulie Sent: Tuesday, September 09, 2008 3:34 PM To: SPSSX-L@LISTSERV.UGA.EDU Subject: paired vs independent samples t-test

Dear all, in pre-test post-test studies where only one group in involved for comparing the means before and after treatment "paired samples t-test" is required. is that right? i was just wondering how can independent samples t-test in such a situation change the results. I mean is it possible to find a mean difference significant with a pairde t-test and insinificant with an independent t-test? cheers Humphrey

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