Fast and effective feedback: are model answers the answer?
A study comparing student responses and performance after receiving feedback both in the form of model answers and personal comments found that while a majority of students wanted both types of feedback, they preferred the personal. However, there were highly significant differences between the mean marks achieved in examinations, with students performing better in model answer questions in both 2004 and 2005. These results suggest that the best approach might be a hybrid one, drawing on the strengths of both kinds of feedback.
Huxham, M. in A & E in Higher Ed Dec 2007