Whenever we have a live training event we want to evaluate how well we did. I have been to a lot of trainings and have seen many ways that people try to evaluate.
Some give you very long surveys and some just focus on a few questions. Some ask about the presenter, the location, the pacing, the content. Some give lengthy tests to see if you actually learned (or can repeat) the information that was presented.
I always wonder how effective these surveys are. Clearly we need to measure the effectiveness of our trainings. 
But do these questions really measure effectiveness?
For a training event to be successful it has to create a change in behavior. But that is really hard to measure, especially at the time of the training. When the training finishes you can't really measure if behavior has changed. All you can do is determine if there is the potential for change.
So, here is one question you can ask at the end of your training session, one question that will let you know if they got enough out of the event to at least create the potential for change:
"When someone asks you what you learned from today's event, what will you tell them?"
That's it. What you are basically asking them to do is to tell you what they would teach someone else about your event. If they can clearly teach what they have been taught then you are well on your way to creating change. But if what they write has very little to do with the change you wanted to create then you probably need to go back to the drawing board.
