My fault, Steven, for not reading the message properly. Even there, you have to specify which gap you are measuring. Is it the gap between what trainees know and need to know, or how trainees perceive the training provided and expected, or what managers expect from their trainees after training and how the trainees perform, etc.?
If you have established parameters and elaborate on what exactly you are after, I am sure experts will guide you.
Regards,
Simhan