1. A method of forming a statistical model for a set of independently variable parameters for timing analysis of a circuit design, the method comprising the steps of: establishing a timing model including delay and delay changes due to process parameter variations (Pi) that impact timing; selecting an element of the circuit design that dominates circuit delay in the timing model, the element being one of a plurality of elements of the circuit design that dominate circuit delay, wherein the plurality of elements consist only of designed minimum width interconnects, the designed minimum width interconnects all having approximately the same linear combination of wire width and wire thickness; determining a delay sensitivity of each of a set of derived process parameters (Vj) for the element that are linear combinations of the process parameter variations (Pi); selecting only those derived process parameters with a high sensitivity for use in the statistical model, wherein process parameters with high sensitivity are determined to be the process parameters with the largest associated Eigenvalues; and forming a statistical model using the derived process parameters with the high sensitivity.