Weighting in AHP (Pembobotan dalam AHP)
Analytical Hierarchy Process mengatasi masalah dengan pendekatan weight (berat) dan scores (nilai). Ini dilakukan dengan menyusun kompleksitas sebagai sebuah hierarchy dan mengukur skala rasio melalui pairwise relative comparisons. Penggunaan redundancy membolehkan prioritas yang akurat diambil dari verbal judgement. Kita dapat menggunakan kata-kata untuk membandingkan qualitative factor dan memperoleh ratio skala prioritas yang dapat dikombinasikan dengan faktor kuantitative.
Dengan menggunakan pairwise comparison process AHP, weight atau priorities didapat dari satu set judgment. Ketika sulit untuk membenarkan weight yang sewenang-wenang ditetapkan, sebenarnya relatif mudah berdasarkan data mentah, pengetahuan, dan pengalaman dari keputusan itu. Weight atau prioritas ini adalah pengukuran ratio level, bukan dihitung.
Diasumsikan kita ingin menentukan the best retail site dalam sebuah area geografi untuk sebuah toko es krim kecil untuk anak kecil dan keluarga. Ada 3 alternative lokasi, yaitu suburban shopping center, main street, dan the mall. Perinciannya adalah sebagai berikut :
This location would cost $75/sq. ft. per month. We would be in the main food area of a major suburban mall with 75 retail shops and three “magnet” stores (Sears and two large department stores). The mall is frequented by teens, young mothers, and families usually on weekend days and weekday nights. There are three ice cream stores at various locations within the mall.
Suburban Shopping Center
A vacant store location that was formerly a pizza shop is available for $28/sq. ft. per month in a neighborhood “strip” shopping center at a busy highway intersection. The area is populated with 45,000 (mostly middle income, young family) residents of a community who live in townhouses and single family dwellings. The strip center is constantly busy with retail customers of the major supermarket chain, a drug store, a hardware store, a hair stylist/barber shop, and several other small businesses sharing the location. No ice cream shops are located in the community
For $50/sq. ft. per month we can locate our ice-cream store in the ground level of a large high rise office and retail complex. The shop would be in a moderately out of the way corner of the building. The majority of the people frequenting the building and the surrounding area are young professionals who are in the area Monday through Friday only. There is one ice cream store within a ten-block radius of this location.
Pairwise comparisons of the elements at each level of an Expert Choice model are made in terms of either:
• Importance—when comparing objectives or players with respect to their relative importance.
• Preference—when comparing the preference for alternatives with respect to an objective.
• Likelihood—when comparing uncertain events or scenarios with respect to the probability of their occurrence.
Pairwise comparisons are basic to the AHP methodology. When comparing a pair of “factors”, a ratio of relative importance, preference or likelihood of the factors can be established. This ratio need not be based on some standard scale such as feet or meters but merely represents the relationship of the two “factors” being compared.
Verbal judgments about the relative importance of each objective are shown in Figure 15. In this example, we judged COST to be moderately more important to us than VISIBILITY with respect to their parent node, the GOAL of CHOOSING THE BEST RETAIL SITE. In other words, it is moderately more important to us to have an affordable location than one that is highly visible. This judgment can be based on our intuition—we know that people will find our shop, due to other factors (promotion, word of mouth, and so on) even if the storefront lacks high visibility; or we can base our judgment on objective data. Our financial analysis, which includes the rent of the sites, makes it clear that COST is more important since we would be in financial difficulty if we were to choose the high visibility location which is very costly. Each objective is evaluated with respect to every other objective in a similar fashion, using relevant subjective or objective judgments. The result of these judgments is a prioritization (or weighting) of the objectives as shown in Figure below.