Abstract: In a data processing system and method, particularly for processing data derived from a gauge which is measuring the thickness of continuous metal strip issuing from a metal processing plant, the value of the measurement data is sampled at successive time instants and the sampled values are processed such as to derive their mean and standard deviations. The successive time instants are randomly or psuedo-randomly distributed in time so as to avoid the possibility of the values of the data samples being affected by, or failing to record, any cyclical variations in the measurement data. The processed data may be used to exert a control function on the processing plant.