5.

Validation and samples of multiple-use models

Model	Internal validation	Cross-validation	External validation
LLP, Liverpool Lung Project; PLCO, the Prostate, Lung, Colorectal and Ovarian.
Bach	Operate the model from five related study sites 3 times	10-fold cross-validation
Spitz (2007)			25% of the data
Spitz (2008)		3-fold cross-validation
LLP		10-fold cross-validation
LLPi	Bootstrap 200 times
PLCO (2009)	Bootstrap 1,000 times
PLCO (2011)	Bootstrap 200 times		44,233
PLCOM2012			37,332
Etzel	156		325
Pittsburgh			3,642
Hoggart			10% of the data