I would find it really useful if there was a type of essay/long answer question where students could submit the answer to a single question and immediately see feedback (as for other question types).
For example, I often create scenario-based quizzes, where students work through a clinical (veterinary) case. After outlining how they would approach each stage of the case, they need feedback before they can progress to the next stage. For example they might be asked which diagnostic tests they would perform and why, and the feedback would explain which tests were appropriate for that case and give the test results, so they can move on to diagnosis. At present I show the feedback using 'description' questions, but this is a bit clunky, and gives them clues (or often the answer) to previous questions, which they can go back and change.
Our quizzes are almost all for self-assessment - the essay questions are not scored and are not manually graded (although keen academic staff do review student answers and provide feedback to the whole student group).
NB we're using Moodle 2.2, planning to upgrade to 2.4 in the summer.
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The Royal Veterinary College