Hi all,
This is an old thread but hopefully it will be read again by someone. I too would be most interest in such a new question type in the questionnaire module.
Visual analogue scales have many advantages over Likert responses types, both from a statistical and a practical point of view. New psychometric models are being developed for them, in the line of Item Response Theory. See for instance:
Noel, Y. & Dauvier, B. (2007). A beta item response model for continuous bounded responses, Applied Psychological Measurement, 31, 47-73.
Noel, Y. (in press). A beta unfolding model for continuous bounded responses, Psychometrika, . http://dx.doi.org/10.1007/s11336-013-9361-1
and the discussion therein on the advantages.
I have written javascript/php code to implement them. Here is an example (in French):
http://yvonnick.noel.free.fr/qst/
I am quite willing to share the code but cannot engage in writing the moodle integration.
Would there be anyone interested in developing this in the Moodle team? That would be great.
Best,
Yvonnick Noel