A method for altering one or more parameters of a measurement system, comprising: a. analyzing a sample using the system to generate values from classification channels of the system for a population of particles in the sample; b. identifying a region in a classification space in which the values for the population are located; and c. determining an optimized classification region for the population using one or more properties of the region, wherein the optimized classification region contains a predetermined percentage of the values for the population, and wherein the optimized classification region is used for classification of particles in additional samples wherein the optimized classification region is determined by: i. creating an elliptical region having a center that is the median of the values generated for the population and whose major axis is some constant C times the standard deviation in the direction of the major axis of the values generated for the population and whose minor axis is the constant C times a standard deviation in the direction of the minor axis of the values generated for the population; and ii. adjusting the constant C until the elliptical region contains the predetermined percentage of the values. wherein the sample comprises one or more additional populations of particles, the method being characterized by performing steps a to c for the one or more additional populations and interpolating an optimized classification region for another population of particles that was not included in the sample, using the optimized classification regions of the population and the one ore more additional populations. a. analyzing a sample using the system to generate values from classification channels of the system for a population of particles in the sample; b. identifying a region in a classification space in which the values for the population are located; and c. determining an optimized classification region for the population using one or more properties of the region, wherein the optimized classification region contains a predetermined percentage of the values for the population, and wherein the optimized classification region is used for classification of particles in additional samples wherein the optimized classification region is determined by: i. creating an elliptical region having a center that is the median of the values generated for the population and whose major axis is some constant C times the standard deviation in the direction of the major axis of the values generated for the population and whose minor axis is the constant C times a standard deviation in the direction of the minor axis of the values generated for the population; and ii. adjusting the constant C until the elliptical region contains the predetermined percentage of the values. wherein the sample comprises one or more additional populations of particles, the method being characterized by performing steps a to c for the one or more additional populations and interpolating an optimized classification region for another population of particles that was not included in the sample, using the optimized classification regions of the population and the one ore more additional populations. i. creating an elliptical region having a center that is the median of the values generated for the population and whose major axis is some constant C times the standard deviation in the direction of the major axis of the values generated for the population and whose minor axis is the constant C times a standard deviation in the direction of the minor axis of the values generated for the population; and ii. adjusting the constant C until the elliptical region contains the predetermined percentage of the values.