That's funny, it looks as if I never got around to posting this when I wrote it in early November...
After my midyear exams I summarised, for each course, the expected number of students answering each possible set of exam questions, given by the quotient of the number of students and the number of possible exams in that course.
Here's the corresponding summary for my finals. This time I'm including detail about the question choices, because it helps make more sense of the value of $E(x)$.
|Micro||8||2, 1 and 1||4, 2 and 2||0.8|