1. A method for determining a probability density function (PDF) of at least one performance metric in regard to an electromagnetic (EM) component of an electronic device or system, comprising the steps of: (a) providing variability information as an input to a simulation of the EM component, for each randomly varying parameter to be considered in determining the PDF for the at least one performance metric, wherein the variability information for each randomly varying parameter comprises a range and a nominal value for the randomly varying parameter, and wherein the simulation is executed by a processor; (b) for all of the randomly varying parameters to be considered, using the simulation executed by the processor to generate a response surface, wherein the response surface is defined over a statistical range for the randomly varying parameter, and as a function of a related variable on which the performance metric is dependent; (c) using a random vector generator executed by the processor to produce probabilities that the randomly varying parameter will be within each of a plurality of different incremental portions of the range provided in step (a), wherein the random vector generator employs a correlation matrix that correlates values of the randomly varying parameter with the related variable; (d) extracting the related variable from the response surface, based upon the probabilities of the randomly varying parameter; and (e) determining the PDF for each performance metric evaluated in regard to the EM component, as a function of the probabilities of each randomly varying parameter, relative to the related variable.