Sensitivity of the weighting summation decision method to incorrect application

The weighting summation decision method is commonly used and misused for multiobjective decisions. The formal requirements of this method are outlined and some of the kinds of errors that are commonly made in applying it are discussed. Monte Carlo simulation is used to assess the potential that five classes of errors have for causing incorrect decisions. An index is developed which quantifies the complexity of decision problems. The simulations demonstrate that complexity can be about twice as important to quality of decisions as are errors in applying the weighting summation.