Within Family Weighting
In Within Family Weighting Mode all the weights in any set of sub-criteria add to 1 and weights can be changed for each set of sub criteria.
The best way to visualize and change weights in Within Family Weighting Mode is to use Weight Charts.
Set Within Family Weighting Mode using the MENU Panel/Weighting.
Within Family Weighting Mode is provided for back-compatibility with earlier editions of V•I•S•A and for use by experts when appropriate. In many cases a more appropriate way to set weights will be via the default Across Tree Weighting Mode.
For a complex Value Tree hierarchy the criteria should be considered in families using Within Family Weighting Mode. The weight assigned to a parent criterion represents the total of the weights assigned to its immediate sub-criteria. Some consistency checks should be done between families.
One way of proceeding is to first of all rank the criteria in a family in order of importance. An effective way of doing this is to consider a hypothetical option which is rated zero on all criteria and imagine that you are allowed to increase just one criterion to its maximum level. Which one would you choose? This will be the most highly weighted criterion.
Imagine now an option having the criterion you have just selected at its maximum level and all other criteria at zero; then select the criterion you would select to raise to its maximum level next - it will have the second highest weight - and so on until all the criteria have been ranked.
It is important to remember that these weights are dependent on the scales being used for scoring as well as the intrinsic importance of the criteria. If an intrinsically important criterion does not differentiate much between the alternatives then it may be ranked quite low. Having established a rank order assign values to the weights by assigning a value of, say 10, to one criterion, possibly the highest ranked, possibly the lowest ranked, and then consider each criterion in turn relative to that one bearing in mind the interpretation outlined above.
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