Generally, the deviation of measured values from their true values. Such errors may be random or systematic. Random errors should have a Gaussian (normal) distribution about the arithmetic mean of the measurements and this should approach the true value as the number of measurements increases. Systematic errors are consistent differences between the true value and a set of measurements, such that their arithmetic mean is displaced from the true value. Thus random errors determine the precision of a set of measurements, while systematic errors limit their accuracy. The use of the isochron is a common method for minimizing dating errors.