Definition
Toyota distinguishes two kinds of problem, and names which one is on the table at the start of structured problem solving:
- Hassei-gata (発生型) — occurrence-type. Something has gone wrong against an existing, known standard. Performance was being met and then slipped, and the job is to close the gap and keep it from returning. This is reactive work: the standard already exists, so the problem is the deviation from it.
- Settei-gata (設定型) — setting-type. No standard has been violated; instead you set a new, higher standard or target where none existed at that level, and the problem is reaching it. This is proactive work: you are raising the bar, not restoring a lost one.
Both run through the same eight-step method, and naming the type in Step 1 keeps a team honest about what it is actually doing — restoring a standard, or reaching for a new one.
Japanese Origin
- 発生 (hassei) — occurrence, something arising or breaking out
- 設定 (settei) — setting, establishing, fixing a value
- 型 (gata / kata) — type, form, pattern
So “occurrence-type” and “setting-type” — the problem that arose, versus the problem you set for yourself.
Why the Distinction Matters
The two demand different thinking. An occurrence-type problem points toward root-cause analysis: a known standard was met before, so something changed, and the discipline is to find and remove that cause. A setting-type problem often points elsewhere — toward idea generation, design, and method development — because nothing failed; you are inventing a way to reach a level never reached before. Running a setting-type problem through pure root-cause tooling can mislead, since there may be no single “cause” to find, only a better method to create.
This maps onto a broader framework: occurrence-type sits with gap-from-standard (“Type 2”) problems, while setting-type shades toward improvement and target-state (“Type 3”) work. The fuller treatment is in Four Types of Problems; here it is enough to know that Toyota applies its steps to both, and that the type changes how you think.
Common Misunderstandings
Assuming every problem is occurrence-type. Much problem-solving training implicitly teaches only gap-from-standard work. Setting-type problems — raising a standard, reaching a new target — are just as real and need a different stance.
Forcing root-cause analysis onto a setting-type problem. When there is no violated standard, hunting for a single root cause can stall a team that actually needs to generate and test new methods.
Skipping the naming. The value is in declaring the type up front, in Step 1, so everyone knows whether the work is to restore a standard or to reach a new one.