PPIG discuss: cognitive dimensions questions

[Marat Boshernitsan]

I have a system that I developed using the Cognitive Dimensions 
framework to guide the design of the interface and of the interaction. 
I am now performing a user evaluation of this systems and I would like 
to include a Cognitive Dimensions questionnaire.  I have found a few 
descriptions of such user-based CD evaluation in the CD bibliography 
(http://www.cl.cam.ac.uk/~afb21/CognitiveDimensions/CDbibliography.html).

At least one of the previous evaluations (Clarke 2001) notes that it is 
difficult to generate numerical data from the user's responses.  So my 
question is whether it makes sense to use a numerical scale (e.g. Likert 
scale) instead of (or in addition to) free-form responses?  What about 
using a notation-neutral questionnaire (Blackwell & Green 2000) vs. a 
notation-specific one, such as the one in Kadoda (2000)?  Would one make 
more sense with a numerical scale than the other?

Thanks!
Marat.
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