A paper I'm reading (Davis-Stober et al, 2014) contains the following statement:
A crowd is wise if a linear aggregate, for example a mean, of its members’ judgments is closer to the target value than a randomly, but not necessarily uniformly, sampled member of the crowd. (p79)
When I googled "linear aggregate" I didn't find any definitions or Wikipedia pages devoted to this concept.
It would be helpful if in addition to a definition the answerer could provide some more examples of linear aggregates, and some examples of nonlinear aggregates.
Davis-Stober, C. P., Budescu, D. V., Dana, J., & Broomell, S. B. (2014). When is a crowd wise?. Decision, 1(2), 79-101.