ABSTRACT
Any investigation of the performance of the human machine requires the taking of measurements and the interpretation of the resulting data. Continuity is used in two senses. In the conventional sense a function is continuous if it does not have jumps in value. Sometimes signals in body are assumed to be ‘on or off’: a good example is the transmission of electrical pulses down a nerve fibre. A deterministic signal is one that can be expressed in terms of a mathematical equation. Such a signal has a predictable value at all times providing its underlying equation is known. The appropriate descriptors used to measure and to compare signals depend to a large degree on the classification of the signal. For continuous signals, with effectively infinitely many sampling points, the problem is reversed. There is now only one mathematical equation that fits the data precisely. It is most unlikely that any convenient and manipulable equation will describe a real measured process.
