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 <a href="search.pl?p=double cross-validation">double cross-validation</a> and the <a href="search.pl?p=jackknife">jackknife</a> are discussed in Armstrong (2001d).<o:p></o:p></P>
 <ul>
   <li>Armstrong, J. S. (2001d), “Evaluating forecasting 
methods,” in J. S. Armstrong (ed.), <I>Principles of Forecasting.</I> Norwell, 
MA: Kluwer Academic Press.</li>
 </ul>