5. Classical decomposition is the second least familiar method. time series Only about one half of the respondents indicated any familiarity decomposition with this method, although it is one of the most useful, since it can distinguish the various subpatterns (seasonality, trend cycle, and randomness) of a data series and can be used to seasonally adjust a data series. Only the Wilson study showed a higher percentage of usage of this method. (Wilson does not report users' familiarity with the various methods.)