Posted by
Larnie on
Aug 06, 2009; 11:06am
URL: http://spssx-discussion.165.s1.nabble.com/Cronbach-s-alpha-tp1089680.html
Hi
I tested a group of 6 parents, who completed a questionnaire, which
contained 15 questions (likert scale response format).
This was part of a pilot study. I used a previously validated measure;
however, the words 'mental health service users' was changed to 'parents
of children with ADHD', to suit my sample. Participants also provided
qualitative data regarding the usefulness of the scale for use with
parents of children with ADHD.
I ran the analysis to determine the Cronbach's alpha for the modified
scale (which will be used in the main study).
Cronbach's was .920
BUT>>>>this warning message comes up on SPSS:
'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.'
and no squared multiple correlations were calculated.
What would have caused this to happen?
Parents felt that a few items needed to be modified for various reasons
(hence their responses to these items were not as expected), could the
problem be related to this?
Can I still use the Cronbach's?
Need help, not a stat guru.
Thanks
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