Date:         Mon, 8 Jun 2009 07:36:38 -0400
Reply-To:     Art@DrKendall.org
Sender:       "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From:         Art Kendall <Art@DrKendall.org>
Organization: Social Research Consultants
Subject:      Re: Reliability Analysis
Comments: To: Jims More <morejims@yahoo.com.au>
In-Reply-To:  <532507.87948.qm@web112607.mail.gq1.yahoo.com>
Content-type: multipart/alternative;

It means that one (or more) item(s) is (are) correlated close to 1.00
with one or a set of other items. I.e., the squared multiple correlation
cannot be computed. Some items are "perfectly" predicted from each other.

Do you have a sufficiently large number of cases after listwise
deletion?  Are any pairwise correlations close to 1.00?
Are you sure no item is included twice in the set of variables for the
scale? Are any corrected item-total correlations very high?
Are there items that make a trivial difference between the overall alpha
and the alpha if item deleted?


Art Kendall
Social Research Consultants


Jims More wrote:
> I am doing reliability analysis for the 20 items (4-point scale).  The
> outputs showed warning which read:
>
>     "The determinant of the covariance matrix is zero or approximately
> zero. Statistics based on its inverse matrix cannot be computed and
> they are displayed as system missing values."
>
> What is the layman meaning of the warning?
>
> On the other hand, the "squared multiple correlation" column is empty
> for all items.  What does it mean?
>
> Thanks you.
> Jims
>
>
>
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