Computer-based tests with randomly generated questions allow a large number
of different tests to be generated. Given a fixed number of alternatives for
each question, the number of tests that need to be generated before all
possible questions have appeared is surprisingly low.Comment: 19 pages; bibliographic information added as follows. To appear in
Bingham, N. H., and Goldie, C. M. (eds), Probability and Mathematical
Genetics: Papers in Honour of Sir John Kingman. London Math. Soc. Lecture
Note Series. Cambridge: Cambridge Univ. Pres
