Abstract : An important aspect of cost research is the measurement of the uncertainty inherent in the projection of system cost. Only recently have approaches utilizing such tools as statistical decision theory and probability theory been formulated. The study described here explores and evaluates three such techniques: (a) The derivation of moments technique employs equations for deriving the moments and distributions for cost elements and aggregations. (b) The Monte Carlo technique is a simulation routine. (c) The symmetric approximation is a special case of the derivation of moments technique.