Circuit design requires devices of different types - NMOS and PMOS transistors - to be closely matched in order to be used in complementary circuits. Matching devices exhibit an identical electrical behavior when discounting for the sign of the electrical currents and voltages. More precisely, the respective threshold voltages are identical. Due to process variations and different process sequences for the N and P type devices, the distributions of these electrical parameters do not coincide automatically. In a fashion similar to the one described in the previous section, statistical simulation can be used to establish a set of nominal process parameters that minimizes statistically the differences between the two groups.