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Pairwise comparison

To rank a list of customer needs, they can be compared two at a time, counting how many times each need "wins". The number of comparisons needed for nn needs is given by the binomial coefficient (n2)\binom{n}{2}, since each pair is judged once.

(n2)=n(n−1)2\binom{n}{2} = \frac{n(n-1)}{2}number of pairwise comparisons for nn items

Symbols

nnnumber of customer needs being ranked

Example

For 6 customer needs, (62)=6⋅52=15\binom{6}{2} = \dfrac{6\cdot 5}{2} = 15 comparisons are needed.

The method grows quickly: doubling the number of needs more than doubles the number of comparisons.
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Part of Product Development: Process and customer needs.