Training is conducted to increase the skills levels of the employees. Skill levels are increased so that employees can execute their job effectively and thereby meet individual measures of performance.
Before training, it is important to do the "Gap Analysis" through pre-training activities. Many training professionals concentrate more on delivery, style etc however, real strength of trainer lies in pre-training activities.
After the training, you can check whether there is increase in measures of performance or not. This increase or decrease of ratios speak in itself everything.
For additional information you may refer my following reply of some previous post:
Dinesh V Divekar