Issue Root Identifier Calculator

Example Data Table

Example rows are illustrative for planning discussions. Use your scoring standards for consistent results.

Formula Used

• RPN (Risk Priority Number) = Severity × Occurrence × Detection.
• Root Likelihood Score (0–100) blends normalized RPN, evidence strength, containment gap, and recurrence.
• Residual Risk (0–100) reduces Root Likelihood Score based on action maturity.

How to Use This Calculator

1. Describe the symptom as an observable effect, not a guess.
2. Score Severity, Occurrence, and Detection using your standards.
3. Rate evidence strength and containment effectiveness realistically.
4. Include recurrence history to reflect pattern risk.
5. Submit to get a priority band and suggested RCA depth.
6. Export CSV/PDF to share with stakeholders and audits.

RPN and the cost of delayed containment

In high‑mix production, small score shifts can create big exposure. Because RPN multiplies Severity, Occurrence, and Detection, moving from 5‑5‑5 to 6‑6‑6 raises RPN from 125 to 216, a 73% increase. Use that jump to justify containment before debating long-term fixes.

If Detection is 7 or higher, add upstream checks, increase sampling, and place a temporary quality gate where the symptom first appears.

Evidence strength improves decision confidence

Evidence strength reduces “loudest voice” decisions. A 1–2 rating means anecdotes; 4–5 means measured data like defect rates, torque logs, calibration records, or environmental readings. Improving evidence from 2/5 to 4/5 reduces false root conclusions and rework.

Capture what supports each hypothesis: Pareto counts, lot traceability, time series, or quick correlation tests. When evidence is weak, run fast experiments and verify the measurement system first.

Containment effectiveness reduces customer risk

Containment is scored as effectiveness, not effort. A 1/5 means leaks are likely; 5/5 means protection is verified. Improving containment from 2/5 to 4/5 often halves downstream defects when controls sit before final inspection.

Validate containment using confirmation sampling and clear release criteria. Document the lot range, owner, and checks to prevent partial escapes.

Recurrence history reveals systemic patterns

Recurrence converts isolated events into pattern risk. A score above 6/10 suggests systemic drivers such as tool wear, training variance, supplier drift, or unstable methods. Compare recurrence by shift, line, and supplier to locate repeat signatures.

Use recurrence to select depth: repeated issues deserve broader cause-and-effect mapping and control-plan updates. Pair recurrence with Occurrence to separate chronic noise from true spikes.

Action maturity predicts residual risk

Action maturity reflects whether countermeasures are standardized, verified, and audited. Mature actions include updated work instructions, poka‑yoke, control charts, and periodic checks. Raising maturity from 1/5 to 4/5 can lower residual risk by up to 20 points here.

Define a verification metric, target date, and owner. Follow up at 30, 60, and 90 days to confirm the fix holds and prevent regression. Sustained review always turns correction into prevention.

FAQs

1) What does the Root Likelihood Score represent?
It is a 0–100 composite blending normalized RPN, evidence strength, containment gap, and recurrence. Use it to prioritize investigation effort consistently across issues.

2) Why is Detection scored higher when detection is worse?
Higher Detection values mean the defect is harder to catch before escape. This raises RPN and highlights weak controls that need earlier checkpoints or improved monitoring.

3) How should we standardize Severity, Occurrence, and Detection?
Use a shared rubric with examples for each score. Calibrate scorers using the same sample cases, then review definitions quarterly to keep scoring consistent.

4) Can this replace a full root cause analysis?
No. It guides triage and depth. For high or critical results, complete structured RCA, validate causes with data, and track corrective and preventive actions.

5) What inputs most improve accuracy?
Strong evidence and recurrence history. Add defect counts, traceability, measurement data, and process conditions so conclusions shift from assumptions to verified causes.

6) How do we use exports for audits?
Save CSV for trend reviews and attach PDF to deviation or CAPA records. Include scoring rationale, containment scope, and verification steps to support audit trails.