The project
You join Tarn Valley Data Science Ltd (simulated company)
You are the junior ML engineer on a member-cancellation model for a chain of fitness clubs. The Senior ML Engineer gives you a ticket, a training extract with planted problems, a plan with mistakes in it and a log of experiments, one of which scored 0.99. Over four weeks you count what is really in the data, prove where the too-good score came from, find that 97 percent accuracy is the baseline, choose a threshold with costs and a call capacity, handle a change request, and then deal with the model after release: a fairness gap, a changed door system, drift and a deletion request.
The people in the story are roles, such as Lead Engineer, not real people.
