What could be a really efficient question after a lecture is "What do you remember of this lecture ?'. With this kind of question we force the public to remember what have been said and to summarize informations. If we add 'What has been forgotten ?', each person will be forced to remember and think by themselve.
Close-ended questions are useful to collect a factual information or when we want to follow a trend. They have the urge advantage to be really easy to analyse, that's why we prefer to use it, even if we use it too much.But, they have 2 big limits.
The question 'What's the weather today ?" isn't one of the closed-ended question to which you can answer : 'nice' or 'not nice'. After all, is the question 'What's the wheather today ?' only a question where you ask for climatic matter ?
Facing digital era, all organizations now know that the status quo is not possible. The most advanced are facing the challenge of training the greatest number. The others realize that they have to make up for lost time.