Sorry my background is in engineering not stats so I probably confused my terms a little. I think I mixed up 'variable' with 'parameter'. As an example of what

Sorry my background is in engineering not stats so I probably confused my terms a little. I think I mixed up 'variable' with 'parameter'. As an example of what I meant, at the plant where I work we are often concerned about yield (the ratio of input mass to output mass). We measure a number of different "terms" during our process which we have control of to varying degrees (As an engineer I call these terms parameters I guess a statistician calls them 'independent variables'). So the term I'm trying to model is yield and my input variables are the various 'terms'. I will read up on cross validation now (hadn't heard of it before). My work uses SAS - a quick google search suggest SAS supports this test. Thanks for answering my question.