ergodicity
n. a principle stating that the average value of a variable over a set of individuals in a defined space or time, such as a sample, will be the same as the average across a long time series of points for a single individual. For example, if ergodicity held for a measure of satisfaction in an organization, the average satisfaction score of all employees in the organization would be the same as the average satisfaction score across a one-year period for one employee. In reality, ergodicity does not always hold, thus giving rise to different streams of nomothetic and idiographic research, which focus on the group or the individual, respectively.