By the end of this lesson you can
- Explain the build-test-learn cycle.
- Plan rounds of testing and iteration.
- Know when a design is good enough to move on.
The idea
Iterative design means improving a design through repeated cycles: design, test, learn, change, test again. Each round fixes the biggest problems and reveals the next layer.
Why small rounds work
Major problems hide smaller ones: if people cannot find the checkout, you will never learn whether the payment form is confusing. Small rounds of about five people, with fixes in between, find more problems overall than one large test.
Planning iterations
- Plan two or three rounds into the project timeline from the start.
- Keep the core tasks the same between rounds so you can compare.
- Add new tasks as the design grows.
- Track issues across rounds: fixed, still present, new.
When is it good enough?
Agree criteria with the team: for example, all critical and serious issues on core tasks resolved and most participants completing core tasks without help. Then ship, measure in live use and keep iterating.
Why it matters in real projects
No design is right first time. Iterating with evidence produces much better outcomes than polishing a single version and hoping. It also reduces risk: problems are found when they are cheap to fix, and stakeholders see steady, measurable progress.
A realistic example
A council's school admissions service goes through three rounds. Round 1: four of five parents cannot find how to rank schools. Round 2: ranking is clear, but three of five misunderstand the deadline. Round 3: the deadline is clear and all five complete the core task, with only minor issues left.
The team agreed in advance that this met their criteria, so they release a beta while monitoring support calls and completion rates.
Step by step
Plan rounds
Schedule two or three test rounds.
Define core tasks
Choose tasks to keep across rounds.
Run round 1
Test and analyse.
Fix the biggest problems
Change the design for critical and serious issues.
Run the next round
Test again and track issues.
Check exit criteria
Decide whether the design is ready.
Common mistakes
Mistake One big test at the end.
Instead Plan small rounds throughout.
Mistake Changing tasks every round.
Instead Keep core tasks consistent to compare.
Mistake No exit criteria.
Instead Agree when the design is good enough.
Check your understanding
Choose an answer, then check it. There is an explanation either way.
Practice exercise
Exercise · about 30 min
Iteration plan
Plan iterations for a project.
Steps
- Define core tasks.
- Schedule three rounds.
- Write exit criteria.
- Create an issue tracker with fixed, still present and new columns.
Deliverable
An iteration plan and issue tracker.
Self-assessment
Tick each item when it is true of your exercise. Be honest; this is for you.
4 items
Summary
- Iterate: design, test, learn, change, repeat.
- Small rounds find more problems.
- Track issues across rounds.
- Agree exit criteria and keep improving after launch.
Further reading
Third-party sources, chosen for reliability. They open in a new tab.
- Parallel and iterative design + competitive testing (opens in a new tab)Nielsen Norman Group
- Why you only need to test with 5 users (opens in a new tab)Nielsen Norman Group
Your notes
Marking complete updates your course and roadmap progress.