01 / Existing systems
Signals and evidence
Inspection, metrology, SPC, maintenance, test, and quality systems remain the systems that collect technical evidence.
For engineers working through unresolved causes
When the defect returns, the investigation should be further ahead.
Recurring defects rarely suffer from a shortage of possible causes. The hard part is building enough understanding to know which explanation is supported — and which is only plausible.
PRIZ guides the investigation. Engineers own the technical conclusions, tests, decisions, and implementation.
The reality of root cause work
A plausible cause can close an investigation too early.
Pressure to act is real. But when evidence, assumptions, and mechanisms blur together, corrective action can begin before the technical explanation is ready.
-
01
The first explanation wins
A familiar or convenient hypothesis gains momentum before alternatives are seriously examined.
-
02
Evidence and assumptions merge
Observed facts, engineer interpretation, and inherited beliefs begin to look equally certain.
-
03
Symptoms become mechanisms
The team names what happened, but not yet how the system could have produced it.
-
04
Action starts before understanding
Corrective action becomes the finish line even when the causal explanation is still incomplete.
An illustrative investigation
A wafer scratch appears after transfer. What would convince you of the cause?
Follow one investigation from observation to a supported engineering direction.
01 / Observe
Separate the observation from the story.
The scratch is real. The explanation is not—yet. Start by making the boundary between evidence and interpretation visible.
PRIZ keeps observations, assumptions, and unknowns distinct as the investigation begins.
Observed
Intermittent scratch after wafer transfer
Known
The scratch is real, intermittent, and detected after transfer.
Still unknown
When the damage occurs and which interaction creates it.
02 / Explain
Keep competing mechanisms alive long enough to test them.
More than one mechanism can fit the same symptom. The useful question is not “Which sounds right?” but “What evidence would separate them?”
Functional Thinking helps connect the observed effect to the interactions that could physically produce it.
Three mechanisms still fit the observation.
What would separate them?
Scratch orientation · pre/post-transfer inspection · tool or slot correlation
03 / Decide
Turn the strongest explanation into a decision the team can defend.
A useful RCA conclusion carries the evidence, the remaining uncertainty, and the next engineering action with it.
PRIZ keeps the rationale connected so the next team can see why the conclusion was reached—not just the label that survived.
Supported explanation
What does the evidence support strongly enough to act on?
Next engineering move
What should the team test, change, or verify next?
Keep the reasoning. Retain the evidence, rejected explanations, and remaining uncertainty for the next investigation.
Value for engineering teams
Make the reasoning useful beyond the incident.
RCA becomes more valuable when the investigation leaves behind a defensible explanation, explicit unknowns, and reasoning the next engineer can reuse.
-
01
Clearer investigations
Evidence, assumptions, hypotheses, and unknowns remain visible as the technical story develops.
-
02
Better technical conversations
Engineers can challenge the mechanism rather than debate disconnected conclusions.
-
03
More defensible solution directions
Options can be understood through the reasoning and evidence that led to them.
-
04
Learning that survives turnover
Future teams can recover context, rejected hypotheses, decisions, and related investigations instead of reconstructing them.
Where PRIZ fits
Alongside the technical systems and methods you already use.
Measurement systems provide evidence. RCA methods help structure questions. PRIZ supports the engineering reasoning that connects evidence, functions, hypotheses, decisions, and retained learning.
02 / PRIZ
Engineering understanding
Evidence, unknowns, assumptions, hypotheses, Functional Thinking, RCA methods, and solution development stay connected as the investigation evolves.
03 / Human-led action
Decisions and implementation
Engineers and leaders determine what the evidence supports, what to test, what to change, and how to verify results.
Questions from engineering teams
Where would this fit in our RCA work?
Does PRIZ identify the root cause automatically?
No. PRIZ helps engineers structure evidence, unknowns, hypotheses, models, and appropriate methods. Engineers remain responsible for technical conclusions and decisions.
Can PRIZ be used with 8D, 5 Whys, and other RCA approaches?
Yes. PRIZ can support the engineering investigation inside broader RCA or corrective-action workflows, and includes methods such as 5+ Whys and Cause and Effect Chain where they are appropriate.
What does Functional Thinking add to RCA?
It directs attention toward what the system must do, how elements interact, and which useful, insufficient, or harmful functions could produce the observed effect.
What if we do not yet have enough evidence to name a cause?
That is a valid investigation state. Making the unknowns explicit helps the team decide what evidence or test would most reduce uncertainty before committing to a conclusion.