I tried implementing zero intervals in the Learning Wizard (Hugin 8.0) for the variable “wtp” (willingness-to-pay for water quality improvement) , using Discretize Manual in the Preprocessor, using the tab-delimited datafile (see attached).

What did I expect as a result? I expected to see the interval 0-0 in CPT for “wtp” with zero probability across all parent states (“user_type”, “dist”, “qual”). As far as I know there are no simulation results for “wtp” exactly equal to zero, but I still need the interval to appear in the CPT with zero probability (I don’t expect Hugin Wizard to drop intervals without observations, but maybe this happens).

Why do I need this? Later I manually create the state “none” for the node “qual” to represent ‘water quality improvement is none’. I then want to attach a 100% probability to a 0-0 interval in “wtp” indicating that there is exactly zero willingness to pay for water quality improvement equals “none”. Without the 0-0 interval I have to assign an equal probability to the intervals -1000-0 and 0-1000 to capture the idea, but I lose information with a “fuzzy zero” of this kind.

This may sound trivial, but it is a key feature of integrating monetary valuation method results with DPSIR modelling in BBNs, and then conducting cost-benefit analysis of decisions.

Can you help?

Kind Regards,

David

P.S. How do I attach Hugin files to this "topic?"