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Date:         Mon, 31 Jul 2006 15:37:27 -0400
Reply-To:     Stephen Brand <sbrand@uri.edu>
Sender:       "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From:         Stephen Brand <sbrand@uri.edu>
Subject:      Re: Cronbach's Alpha if item deleted
Comments: To: Steph Auty <stephanie.auty@IPSOS-MORI.COM>
In-Reply-To:  <200607311500.k6VAkGRi016332@mailgw.cc.uga.edu>
Content-Type: text/plain; charset="US-ASCII"

Steph,

If the increment in alpha is very small, you might want to use this information to shorten your measure in future studies. The benefit of cutting the item is not so much that alpha goes up but that you make the survey go faster for the participants without losing information.

HTH,

Stephen Brand

Stephen Brand, Ph.D. Associate Professor (Research) NCPE-SP, University of Rhode Island Kingston, Rhode Island

-----Original Message----- From: SPSSX(r) Discussion [mailto:SPSSX-L@LISTSERV.UGA.EDU] On Behalf Of Steph Auty Sent: Monday, July 31, 2006 11:00 AM To: SPSSX-L@LISTSERV.UGA.EDU Subject: Cronbach's Alpha if item deleted

Hi,

I am using Cronbach's alpha to test the reliability of an index I want to create. I am getting values of around 0.9 which I am very happy with, but sometimes SPSS says that alpha would be improved if I removed one of the variables. What sort of cut-off point should I use for this? Some of the improvements are very small (e.g. 0.002). Is it worth removing these questions?

I have several datasets each asking a range of questions which overlap quite a lot. In one case, even though an improvement is very small, it would make an improvement to remove it in every dataset which uses it. Would this mean I should remove it even if just looking at one dataset I wouldn't?


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