[R] OT: single measure of (group) correlation with more than two vectors?

[context grey]

Hello, 

I have a survey in which a number of people rated a
set of items on a 
1..5 scale.  I believe it would be desirable to argue
that the
people's responses are correlated, and thus that the
rating task
makes sense to people.

Is there a standard approach to this?   With only 2
people,
the correlation coefficient between their responses
would
be an interpretable number, (though probably there is
some
stronger way to assess whether the results are
_significantly_ correlated).

With N>2 people, there is the correlation matrix, but
it does not
give a nice single number.  Thinking, the determinant
of
the matrix of response vectors might be a possibility,

since it will be low if the rows are correlated.
Though, it should be normalized somehow to be
interpretable.

Is there a standard approach to this problem?

Thanks for any advice




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