### Probability A/B – ST111/2 Exam Reflection

Probability was the first Maths exam I took this term, on the 31st. I had a bunch of past papers, but the lecture notes were still incomplete. No answers were provided for any assignment bar the last, but I got most of the marked questions right, and probably most of the rest of the questions as well.

I did…around 3 past papers of the old style, and one or two newer ones. I skipped some of the questions of PGFs and the like that aren’t in the syllabus. Before the exam, I felt like I’d done enough revision – more that I didn’t feel like doing any more.

The exam itself was split into two parts: A and B. A bore some resemblance to past papers but had a fair few questions on the theory, the like of which hadn’t come up before. I was glad I picked Games & Decisions at this point, as the extra work on basic probability helped.

I think I did pretty well on Prob A, overall. I was able to answer all of the questions, which is a good sign. I wasn’t exactly sure what “basic set operations” were, though, especially when Probabilities are added to the mix.

Probability B was different. I couldn’t remember how to find joint or marginal densities, the version of Markov’s inequality was different to the one I knew, and I thought that a question asking for an expected number of offers relating to “a” (nonspecific) cdf F meant to average over all possible cdfs, so one question was right out. 4 past paper sub-questions came up, so that was very convenient. Couldn’t remember exactly how to find P(X < Y) given distributions, did a double integral that seemed reasonable at the time.

Overall, I think this exam went very well, although as it was the first I did more revision on it than I have for many other subjects (there were more past papers available, too). I think I did *too much* revision – I could quite easily have done substantially less and got a similar mark. I am planning on doing more Stats later, though, so no harm.

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