Prototype Fidelity Ladder: Defect Detection vs Cost

Fidelity Stage

Stage: Paper Mockup

Team rigor (test thoroughness) 1.0×

Readouts

Total cost

Total time

0.0 d

Defects remaining

10 / 10

Confidence

How it works

Every fidelity stage of a prototype — paper mockup, digital CAD model, 3D-printed part, functional build — resolves hidden design flaws with a different probability of detection (POD), a real concept used in inspection and non-destructive testing. Higher fidelity reveals more, but costs more and takes longer per test round.

P(detect one round) = 1 − e^(−k · r)
  k = stage inspection-power constant
  r = team-rigor multiplier (0.5× – 2.0×)

Ten defects are seeded on the bracket at fixed positions. Each Run Test Round gives every still-hidden defect an independent Bernoulli trial at that probability; found defects turn green permanently. Cost and time accumulate per round at the current stage's rate:

Paper:      k=0.15  $5/round   0.5 day/round
Digital CAD:k=0.35  $40/round  1 day/round
3D-Print:   k=0.65  $150/round 2 days/round
Functional: k=1.10  $600/round 4 days/round

Fidelity stage buttons — swap the bracket's material/geometry detail and change the detection-power constant k used by the next test round.
Team rigor slider — scales k, modelling more careful (or rushed) inspection at any given fidelity.
Confidence — the fraction of the ten seeded defects already found; it is the real-world proxy for "how sure are we this design is ready to ship".

This is the actual trade-off product teams reason about when deciding how far to push a prototype before committing to tooling: catching a flaw on paper costs a sketch; catching the same flaw after tooling a functional unit can cost weeks and thousands of dollars.

Undetected defect Found defect

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