Example. Three attainable protocols with different scalar, Pareto, and worst-group summaries [ftip-005S]

Three attainable utility vectors separate the answers returned by scalarization, Pareto comparison, and a worst-group summary.

For scalar weights \((0.8,0.2)\), the scores are \(S(A)=0.80\), \(S(B)=0.70\), and \(S(C)=0.56\), so \(A\) wins. The worst-group scores are \(0.4\), \(0.7\), and \(0.5\), so \(B\) wins. No point dominates another coordinatewise, hence the Pareto summary retains all three.

The scalar, Pareto, and worst-group summaries were defined in Definition [ftip-005P]--Definition [ftip-005R]. Their non-equivalence is explicit in these three points, while the choice of a social or evaluation rule remains open.