STK4021 - Applied Bayesian Analysis

Semester page for STK4021 - Autumn 2025

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exercises for Week 4 (Mon Sep 8 ff) and Week 5 (Mon Sep 15 ff)

Wed Sep 10: Exam 2021, #2, #4, Exam 2017, #4. 

Nils is at a Human Rights in Adacemics conference on that day, but you should absolutely meet up: Kushagri Tandon will take you through these three earlier exam exercises (and I'll make sure that *something* from these will turn up, one way or another, for the December 2025 conference). 

Next couple of weeks: Story #17 (cigarettes & cancer); rest of 7.19; hack you way through 7.21 (normal-normal is nice and clear with known sigma, more messy bot doable with unknown sigma); 7.23, then 7.24 Jeffreys (with examples) and after that again 7.29 Nils-Emil vip-Jeffreys. We'll also fill up with more from earlier exam, earlier Oblig, earlier exam projects.

https://dnva.no/detskjer/2025/05/symposium-menneskerettigheter-og-akademisk-frihet

Sep. 8, 2025 10:17 PM
Magic and Supremely Nonmagic Squares

In connection with Story #85, an MCMC take on Magic Squares, I've uploaded com5d to the site. Use it, play with it, constuct magic squares of sizes 4 x 4, 5 x 5, 6 x 6, perhaps higher. This is achieved via the MCMC for f(x) = \exp[-\lambda Q(x)] / constant, with positive \lambda. You may also play with *negative \lambda*, to encourage outcomes as far as possible from magic-ness: sums of rows, columns, diagonals, far away from the magic number (34 for 4 x 4, 111 for 6 x 6, etc.). The exercise is then to find the Bayesian MAP, maximising Q(x) as score: the worst ever squares. 

I think it's pretty hard to do this by pure math -- so run chains and see what happens. My current guesses, for 4 x 4 and 6 x 6 (after tne minutes of playnig) are 114 and 540. If you can beat these numbers, tell me, and I'll give you tyve kroner (les Rudolf Nilsen).

Sep. 4, 2025 11:16 AM
exercises Week 4 (Mon Sep 8 ff) and Week 5 (Mon Sep 15 ff)

(Text below is being edited as we do more, so to speak, so read also updates.)

We've done (more or less): Ch7 exercises 1, 2, 3, 4, 5, 9, 12, 13, 15, 16, 17; then Stories #41 (Odin's children, Bayesian part), #13 (antidrepressant, Bayesian part), #54 (Star Trek, Bayesian part), #85 (Magic Squares). Up soon, start working: Story #31 (counting hjort, Bayesian part), #17 (cigarettes). 

Tentative plan Mon Sep 8: Story #31 (counting hjort, Bayesian part); more on 7.18, 7.19; Oblig 2021, #2, Exam 2017, #1. 

Wed Sep 10: Exam 2021, #2, #4, Exam 2017, #4. 

Links to these exam & obig sets are on the vevside. Note, and be happy about it, that we're *already* able to do various earlier exam, exam project, oblig problems. 

Sep. 2, 2025 2:21 PM
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