One of the problems faced by the teacher or trainer is trying to ensure that the learning environment created within the context of the learning materials is the best it can be every time those materials are delivered to the learners. But as all teachers and trainers know, materials which work with one group of learners on one day, might not work with another group the next day. It's only through experience that the teacher is able to 'adjust' the plan to enable better learning to take place.