Abstract: Methods of making classifications. One method acquires groups of data, derives features of potential interest in a first data group, and analyzes features using a classification tree and a statistically based classification process to draw a classification conclusion on identity with an associated level of confidence. Features associated with a signal of potential interest may be derived with at least a second group of data. A statistical algorithm may perform linear discrimination analysis, or a quadratic discrimination analysis or a logistic regression classification analysis. A related method includes acquiring signal data with a sensor device comprising piezo-electric material and detecting a signal by performing detections on signal data from the sensor device. Determinations are provided when detections surpass defined thresholds of confidence.