The big idea: Models, prototypes and mock-ups are built to generate performance data when tested with end-users — not to show what the product will look like.
Choose the fidelity from the question, and build only as much as that question needs.
Cost rises with fidelity and willingness to change falls. That pair of curves is the whole argument for low early and high late.
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| The question | The model that answers it | The data it produces |
|---|---|---|
| How far must the surface reach over the bed? | Card and foam at full size, on any column | A distance, from 8 patients miming the reach |
| Where do users put their hand? | A printed arm with a real pivot | Hand positions and effort, from 12 users swinging it |
| Does it tip under a realistic load? | Working prototype in the intended materials | Whether a wheel lifts at 5 kg placed 50 mm in |
| Is the mechanism cleanable? | A mock-up of the joint alone, in the real materials | Time taken and whether soil remains after cleaning |
A mock-up of one part is often enough: You do not always need a whole product. The cleanability question is about one joint, so build the joint.
Partial models are cheap, fast, and they isolate the thing you are actually testing.
See how examiners mark answers
Access past paper questions with model answers. Learn exactly what earns marks and what doesn't.
Designing the test, not just the model
Decide the measurement first
Distance, time, count, load, or a rating. Decide before the users arrive, or you will come away with impressions.
Give a task, not an opinion prompt
"Get yourself a drink using this" produces behaviour. "What do you think of it?" produces politeness.
Do not help, and do not explain
Every time you explain, you delete the finding. Write down what they tried instead.
Record against the criterion
The criterion said 5 kg at 50 mm and under 5 seconds. Record exactly those, so the result plugs straight into the evaluation.
A prototype is not the product: A printed part is weaker across its layers than a moulded one, and a card model has no weight.
Say what your model could NOT test. An evaluation that claims more than the model could show is worth less than one that names the limit.
How this is tested — creating models at appropriate fidelity that generate performance data with end-users. It comes up two ways:
Paper 1 — multiple choice
- Pick the fidelity that suits a stated question.
- Identify what a given model could not test.
Paper 2 — analysing a product
- Justify the models used at stages of a named product's development.
- Explain how a test with users produces performance data.
The trap: Building a beautiful final model and testing it once. The marks are for models that produced DATA, at a fidelity matched to the question being asked at the time.
Justify the models a team should build to test a swinging bedside table surface for reach, for hand position and for stability.
Model answer plan
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