Changing from AHP to ANP thinking
- 1. The Analytic Network Process Decision Making with Dependence and Feedback
- 2. Changing from a Hierarchical Model to a Network Model
- 3. Network Models do not have Goals A network model has a criteria cluster and an alternatives cluster, but no goal. Step 1. Compare the alternatives with respect to each criterion (like we do in AHP models).
- 4. Establishing Priorities for Criteria In AHP one answers the question: “How important is Criterion1 compared to Criterion2 with respect to the goal?” Sometimes too abstract a question to answer. In ANP criteria are prioritized by asking how important they are in the alternatives being considered. Usually an easier question to answer when looking at actual alternatives that have the properties in question.
- 5. Cars compared with respect to Prestige (and similarly for the other criteria) .707 .070 .223
- 6. Feedback: Link Alternatives to Criteria and compare for Preference For example, a pairwise question would be: “For the Acura TL, which do you like better, its prestige or its price?” ; “Its prestige or its MPG?” etc. .499 .066 .079 .355
- 7. Make Comparisons For each car pairwise compare the criteria for importance to establish the priorities of the criteria in that car: Prestige, Price, MPG, and Comfort This results in a vector of priorities of the criteria for each car.
- 8. Pairwise Compare Criteria for each Car Acura TL Results for Acura TL Results for Toyota Camry Toyota Camry
- 9. Pairwise Compare Criteria wrt Cars Honda Civic Results for Honda Civic
- 10. The Unweighted Supermatrix For example, the priorities in the last column come from comparing the criteria with respect to the Honda Civic. That is, what we value most about the Honda is its price.
- 11. Limit Supermatrix The limit supermatrix is obtained by raising the weighted supermatrix to powers until it converges (in this case all columns are the same, though not always true). The final answer, the synthesis, below is obtained by normalizing the raw values for the alternatives from the limit supermatrix: ANP AHP Acura TL .457 .344 Toyota Camry .173 .200 Honda Civic .369 .455
- 12. Why are the results different? •In AHP – the user, going top-down making comparisons, when asked without referring to actual alternatives, over-estimated the importance of cost. •In ANP – the user learned through feedback comparisons that his/her priority for Cost is not nearly as high as originally thought when asked the question abstractly, while Prestige gets more weight. This is why a husband and wife, setting out to the dealership to buy a “sensible” low priced car, walked out with something entirely different and much more costly. When they saw the shiny cars on the showroom floor they revised their priorities.
- 13. Inner and Outer Dependence •Outer dependence - the parent node and the nodes to be compared are in different clusters. A directed link appears from the parent node cluster to the other cluster. •Inner dependence - the parent node and the nodes to be compared are in the same cluster. The cluster is linked to itself and a loop link appears.
- 14. We can add some inner dependence: eg, price is influenced by prestige and comfort; and prestige is influenced by price and comfort.
- 15. An Example of an Inner Dependent Comparison is shown below: Which influences Price more, Prestige or Comfort? Which influences Prestige more, Price or Comfort?
- 16. The results with the interdependencies in place are: ANP ANP AHP (With inner (No inner dependencies) dependence) Acura TL .487 .457 .344 Toyota Camry .182 .173 .200 Honda Civic .331 .369 .455