Interactive guide
Make the Decision Without Faking Certainty
A decision system almost never fails by returning an answer somebody can immediately see is wrong. It fails by returning an answer that looks exactly like a good one.
A required field was empty, so the calculation treated the absence as a bad signal instead of a missing one. A score of 20 gets read as “a bit unhealthy” when it actually means “no meeting in four months and these are all email points.” A confidence figure of 0.9 gets treated as a nine in ten chance of being right, which is not what it measures. Every one of those produces a plausible number, and none of them announces itself.
You will build a Decision Design: the shape the decision takes, deterministic rules doing the work they are good at, a model used only where interpretation genuinely helps, an explicit answer for missing and conflicting evidence, an honest confidence policy, one consistent output shape, and a test set of awkward records that has actually been run. The lab saves your progress in your browser.
Start with a broken answer
Pick the Right Decision Shape
Chapter 1 of 8 · 12 min
The learning path
Every chapter starts from a plausible wrong answer and works backwards to whatever produced it. An empty field read as a bad signal. A score of 20 that means two unrelated things. A confidence figure that measures something other than what the person reading it assumes.
Choosing how the answer gets made
- 01Pick the Right Decision ShapeChoose between classifying, scoring, ranking, and recommending, and know what each can and cannot answer.12 min · exercise
- 02Apply Simple Rules FirstDo the deterministic work first, and let one condition short-circuit the rest.14 min · exercise
- 03Use AI Where Interpretation HelpsDraw the line between what a rule can check and what needs reading, and put the model on one side of it.14 min · exercise
- 04Handle Missing and Conflicting EvidenceStop absence being read as a bad signal, and decide which source wins when two disagree.14 min · exercise
Surviving contact with reality
- 05Treat Confidence CarefullySay what a confidence number does and does not mean, and keep a composite score’s parts recoverable.12 min · exercise
- 06Return a Consistent ResultReturn the same shape every time, carrying what the next guide needs to explain it.12 min · exercise
- 07Test Plausible Edge CasesBuild the test set from real failures, and give a population that behaves differently its own rules.14 min · exercise
- 08Capstone: Run the Qualification SetRun every design section against a full set of records at once.15 min · exercise