Translating measurement uncertainty into terms of effective impact associated with
manufacture, testing and incorrect assessment gives a more “stakeholder” motivated (and
ultimately optimised) approach to decision-making in conformance assessment. Recently
developed decision-theory tools include the “optimized uncertainty” methodology and the
“operating cost characteristic”. Overall costs, E, consisting of a sum of
testing costs, D, and the costs, C, associated with
customer risk, can be calculated with the expression:
with
, where
RPV denotes the region of permissible
values and σ is a measure of dispersion. A complete, 3D surface of
overall cost can indicate the optimum level of measurement effort of these two ranges, as
recently published by the author in a wide range of applications: optimized acceptance
sampling; optimized testing of measurement instruments; and an analysis of optimised
calibration intervals and “guard-banding”. This approach is illustrated in the present
work for the example of geometrical product control in the car industry, specifically the
gap in vehicle closure panels taking account of customer dissatisfaction.