Quiz

On a quiz, one of the problems is an essay type answer, where students are supposed to enter a mix of technical text, and equations + numbers. I want to find out if there is any plugin available which can be used to compare student responses and tell the instructor about the likelihood that part or all of the answer was copied from another student, or has common features that warrant further investigation. It is impossible to specify this completely as I am looking for any helpful tool that could help. Needless to add, the essay type question will be manually graded, so something that generates a summary map pointing to attempts of concern would be most helpful. The instructor has to obviously exert the final judgment, but a supportive tool is helpful when you have a very large number of students, and by the time you are grading the 133rd attempt, you have mostly forgotten about the 15th. I have looked at the auto-graded essay type question and that is not what I want. The bigger concern here is students copying from each other, rather than from some known source(s).