Since the shelf exams are national standardized tests, I am fairly confident this info is consistent among US medical schools, but at least at my school, the NBME shelf exams are 100 questions long, and we typically have 2 hours and 10 minutes to complete the test (works out to something like 1 min 20 sec per question). They are written multiple choice exams, but unfortunately, questions with answer choices A-J or A-T are not uncommon. Your score will be reported as an NBME percentage (which, given that there are 100 questions, I have always assumed to be a gross number of correct responses) as well as an NBME national percentile...that is, how you did in relation to other students who took the test nationlly during your rotation. Not surprisingly, as the year progresses, the same percentage score may correlate to a lower percentile, as the collective group of students did better on the test in say, April, than the group in August did. However, we have been told that the 5th percentile nationally is passing (although it may take a higher percentage correct to get in the 5th percentile as the year progresses), although this may differ among schools. I think the shelf exam scores are typically back in two weeks or so, but your grade for the clerkship will probably take longer, as things like written evals will take longer to come in, but you can probably get your shelf score from the clerkship director if you would like.
Hope this helps.
