“Squishy” problems and quantitative methods

The edited text of a talk on potential hazards in the application of quantitative methods to “squishy” problems without well-defined structure, of the type frequently encountered in government policy and decisionmaking. Squishy problems are defined, and a three-level conceptual model of analysis which displays the relative roles of logical inference and qualitative human judgment is described. Two ways in which people use models of all types, as a surrogate for the substantive problem (e.g., Newtonian mechanics as a surrogate for “real” mechanics), and as a perspective on the problem (e.g., two-dimensional perspective drawing) are described and contrasted, and some of the implications of the difference for the analysis of squishy problems are discussed.