[clinic · EX-18] Solve abstention

[akash-coded]

Exercise clinic. One long-running thread per exercise. Ask here rather than opening a
new thread — the answers accumulate where the next person will look for them.

Exercise: EX-18 — Solve abstention · difficulty ⚫

What this exercise asks

Read the exercise first; this thread is for when you are stuck, not instead of it.

Three ways people get stuck on this one

1. Trying yet another score threshold. The repo has measured four and they sit near chance — see finding 3 in the README.

2. Evaluating on a class-balanced subsample, which flatters precision (#7).

3. Optimising F1 without saying what the asymmetry is. A confident wrong answer and a refusal are not equally bad, and the ratio decides the operating point.

How to ask here

Post the numbers you got, the config that produced them, and what you already tried.
A question with a measurement in it gets answered in one round trip; a question without one
takes three.

If you have finished it, post the write-up in Show and Tell with the
[solution · EX-18] prefix rather than here — this thread stays for people who are stuck.