From grimoire
Maps all potential causes of a problem across 6 standard categories (Machine, Method, Material, Man, Measurement, Environment) to prevent single-cause fixation. Use before 5 Whys to identify which causal category to investigate.
How this skill is triggered — by the user, by Claude, or both
Slash command
/grimoire:apply-fishbone-diagramThe summary Claude sees in its skill listing — used to decide when to auto-load this skill
Map all potential causes of a problem across 6 standard categories (Machine, Method, Material, Man, Measurement, Environment) in a visual cause-and-effect diagram — surfacing the full landscape of contributing factors before selecting which root cause to investigate, preventing the premature single-cause fixation that makes problems recur.
Map all potential causes of a problem across 6 standard categories (Machine, Method, Material, Man, Measurement, Environment) in a visual cause-and-effect diagram — surfacing the full landscape of contributing factors before selecting which root cause to investigate, preventing the premature single-cause fixation that makes problems recur.
Adopted by: Standard tool in ISO 9001 quality management systems (adopted by 1M+ certified organizations globally). Required technique in Six Sigma DMAIC (Analyze phase) — used at GE, Motorola, Toyota, Boeing, and virtually all Fortune 500 manufacturing and service operations quality programs. Ishikawa's original application was at Kawasaki Steel; the technique is now standard in healthcare quality (Joint Commission hospital accreditation), software engineering retrospectives, and food safety (HACCP protocols). The ASQ (American Society for Quality, 80,000+ members) includes it in the core quality tools body of knowledge. Impact: Ishikawa (1968) documented application at 230+ Japanese factories where structured multi-cause analysis reduced defect recurrence rates by 40–60% compared to single-cause investigation. Toyota Production System documentation credits fishbone analysis as a key tool in achieving defect rates 10× lower than Western competitors in the 1980s (J.D. Power quality studies). The mechanism: single-cause investigation produces fixes that address symptoms; systematic cause mapping across 6 categories identifies systemic causes — which are 3–5× more common in recurring defects than proximate causes (Juran Institute data). Why best: The 5 Whys (a complementary tool) drills deep on one causal chain; the fishbone maps wide across all possible cause categories. The two tools are used in sequence: fishbone first to identify which causal category to investigate, then 5 Whys to drill into that category. Using 5 Whys alone without a fishbone risks drilling deep on the wrong cause — a common failure mode in process improvement. The alternative (brainstorming without structure) produces unorganized lists where systemic causes get overlooked in favor of recent or visible events.
Sources: Ishikawa (1968) "Guide to Quality Control"; ISO 9001:2015; ASQ Body of Knowledge; Juran & Godfrey (1999) "Juran's Quality Handbook"
Write a precise, specific problem statement and place it at the right end of a horizontal arrow (the "spine"):
┌─────────────┐
─────────────────────────────────────────→ │ PROBLEM │
└─────────────┘
Good problem statement:
✅ "Defect rate on Assembly Line 3 increased from 0.8% to 3.2% in March"
✅ "Customer complaint rate for product X increased 40% in Q1"
✅ "Server response time exceeds 2s for 15% of requests since the v2.4 deploy"
❌ Too vague: "Quality is bad" / "System is slow" / "Customers are unhappy"
The specificity of the problem statement determines the quality of the analysis. Vague problem = vague causes = ineffective fixes.
Draw 6 diagonal lines branching off the spine — the standard 6M categories:
MACHINE METHOD
\ \
\ \
──────────────────────────────────────→ [PROBLEM]
/ /
/ /
MATERIAL MAN
(also: MEASUREMENT and ENVIRONMENT as additional branches above/below)
The 6M categories:
For service/software contexts, adapt to 8P: People, Process, Policy, Procedure, Place, Product, Price, Promotion — or use the 6M as written, relabeling as needed.
For each of the 6 branches, ask the team: "How could [this category] contribute to [the problem]?"
Example — Machine branch for "server response time >2s":
- Underpowered database server (CPU throttling)
- Memory leak in application process
- Network interface at 90% capacity
- Disk I/O bottleneck from logging
Example — Method branch:
- No query optimization in new endpoints
- Synchronous calls where async would work
- No caching layer for frequent reads
Write each cause as a sub-bone branching off the main category line. Add sub-sub-bones for causes of causes.
After populating all 6 branches:
Priority scoring:
High votes + verifiable data + timing correlation = investigate first
High votes but no timing correlation = contributing factor, not root cause
Low votes = deprioritize unless no other candidates
For each top candidate, apply apply-five-whys to drill into the causal chain:
Fishbone identified: "No query optimization in new endpoints"
5 Whys:
Why? → New endpoints were shipped without performance review
Why? → Performance review was not in the deployment checklist
Why? → Checklist was created before performance requirements existed
Why? → Performance SLAs were added after the initial process design
Root cause → Process documents not updated when requirements changed
The fishbone tells you WHERE to look. The 5 Whys tells you WHY it happened.
Document format:
Problem statement: [specific, measurable]
Fishbone diagram: [attached image or drawn]
Top 3 root cause candidates: [listed with evidence]
Selected root cause for action: [one specific cause]
Action taken: [specific corrective action with owner and date]
Verification: [how we'll confirm the cause is resolved]
npx claudepluginhub jeffreytse/grimoire --plugin grimoireApplies Fishbone (Ishikawa) diagrams and 5 Whys to identify root causes of problems and recommend corrective actions. Outputs as YAML or Mermaid diagrams.
Five Whys, fishbone diagrams, identifying systemic causes not just symptoms.
Investigates root causes of defects or incidents by iteratively asking 'why' to trace failures from symptoms to systemic causes. Useful for postmortems and recurring failures.