Students need to pass some tests and interviews to be allowed in Cambridge. For undergraduates, the application is done through UCAS. This is as with any other university in the UK. Students need to be very good to enter Cambridge. If they study A-levels, they are asked to get at least A*AA. Because many good students apply, the interview is very important to choose the best ones. These are done by Fellows. Usually about 25% of the applicants get a place. However, the number changes depending on the subjects. Some of them, like medicine and economics are very hard to get into. Students need to choose a college before doing the application. They may later have to change it if the college thinks they are good but does not have enough places for them.