I'm surprised he didn't use other resampling (e.g. http://en.wikipedia.org/wiki/Resampling_%28statistics%29 http://en.wikipedia.org/wiki/Resampling_%28statistic

I'm surprised he didn't use other resampling (e.g. http://en.wikipedia.org/wiki/Resampling_%28statistics%29 http://en.wikipedia.org/wiki/Resampling_%28statistics%29) techniques to validate the models. Not that resampling is a perfect answer, but...