A test of validity that consists of splitting the data using probability sampling, estimating the model using one subsample, and testing it on the remaining subsample. More elaborate approaches such as jackknife are discussed in Armstrong (2001d).
Armstrong, J. S. (2001d), “Evaluating forecasting
methods,” in J. S. Armstrong (ed.), Principles of Forecasting. Norwell,
MA: Kluwer Academic Press.