Key Idea: A system is parts connected so each responds to the others. Adding more of something is absorbed; changing what is measured or rewarded is what holds.
Paper 1
- Part a: define a system, or identify the shapes of change
- Part b: explain why a previous fix did not last
- Part c: evaluate a proposed solution
Paper 2
- Q1 and Q2: read and evaluate a chart in a source
- Q3: compare sources that model a problem differently
- Q4: synthesise sources on a repeated failure
Everywhere else
- HL Paper 3: every recommendation needs a 'what pushes back'
- Models and charts appear as sources in every Paper 2
- Feedback explains recommender drift and data-driven policing
Five words for describing a system
| Word | What it means | Why it earns marks |
|---|---|---|
| Elements | The parts you can point at | Sets up everything else |
| Connections | What passes between them | Most answers leave it out |
| Boundary | What counts as inside | Decides what may change |
| Purpose | What it reliably produces | Not what it claims |
| Feedback | Output returning as input | Explains why it drifts |
“The stated purpose is X; the purpose its behaviour shows is Y.” It is a serious claim, it is usually true, and it is exactly the analysis part c wants.
Three shapes of change, three different fixes
Name the shape before proposing anything
- Steady — something pushes back, so a one-off effort is absorbed. Only a change to what pushes lasts.
- Growing — each round is bigger, and no single step looks unusual, so it is almost always noticed late.
- Tipping — pressure builds invisibly, then the system flips and stays flipped. Removing the cause does not undo it.
Important: Never ask whether a model is accurate — all models are inaccurate. Ask what it left out, and whether that thing matters for the question being asked of it.
Exam-style questions
Suggest two reasons why an organization might draw the boundary of a problem narrowly.
🔒 Model answer plan
See the mark-by-mark plan — for / against / judgement, with marking guidance — in study mode.
Justify the claim that a visualization should be treated as an argument rather than as evidence.
🔒 Model answer plan
See the mark-by-mark plan — for / against / judgement, with marking guidance — in study mode.
Quick check
What makes parts a system? Each responds to what the others do, so the whole behaves in ways no part does alone.
Why do fixes get absorbed? The other parts change their behaviour in response, often returning the system to where it began.
How do you find a purpose? Read it from what the system reliably produces, not from what its owner says it is for.
The test for a model What did it leave out, and does that matter for this question?
Exam tips
- Add “what will push back is…” to every recommendation. It is the cheapest mark in the paper.
- Name the shape of the change before arguing about timing.
- For any chart in a source, ask what the axis starts at and what is not plotted.