Mohamad-Ali Salloum is a Pharmacist and science writer. He loves simplifying science to the general public and healthcare students through words and illustrations. When he's not working, you can usually find him in the gym, reading a book, or learning a new skill.
Understanding Root Cause Analysis: The 5 Whys and Fishbone method
Mohamad-Ali Salloum, PharmD • February 10, 2026
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When problems happen in clinical research—or any industry—the worst thing we can do is fix only the surface issues.
Real quality improvement comes from understanding why the problem happened in the first place.
That’s where Root Cause Analysis (RCA) tools come in.
Two of the most widely used and easy-to-learn RCA tools are:
The 5 Whys
The Fishbone Diagram (Ishikawa Method)
Both methods help you dig deeper than the symptoms, find the real cause, and prevent the problem from coming back.
🧠 1. The 5 Whys Method
The 5 Whys is exactly what it sounds like:
You ask “Why?” several times (usually 5) until you reach the root cause.
It’s simple. It’s powerful. And it prevents misleading “quick fixes.”
✔ How It Works
- State the problem clearly
- Ask why it happened
- Take the answer and ask “why” again
- Repeat until you uncover the true root cause
- Create corrective and preventive actions
🔍 5 Whys Example (Clinical Research Scenario) — expand
Problem:
The site failed to report an SAE (Serious Adverse Event) within 24 hours.
Why #1:
The coordinator didn’t notice the hospitalization note.
→ Why?
Why #2:
Because the source documents were not reviewed for AEs that day.
→ Why?
Why #3:
Because the coordinator is covering multiple studies and was overwhelmed.
→ Why?
Why #4:
Because there is no workload distribution or backup assigned.
→ Why?
Why #5:
Because the site lacks an SOP for daily AE review and staffing backup.
🎯 Root Cause:
No structured process or backup for reviewing AEs daily.
✨ What this reveals:
The real issue is NOT that the coordinator “forgot”;
it’s a system weakness in staffing and workflow.
🐟 2. The Fishbone Diagram (Ishikawa Method)
The Fishbone method helps you brainstorm possible causes by categorizing them.
When drawn, it looks like a fish skeleton—hence the name.
It's incredibly useful when the problem is complex and may have multiple causes.
✔ The Six Main Fishbone Categories
Most industries use these standard six:
- People – training, workload, roles
- Process – SOPs, workflows, inefficiencies
- Materials – forms, documents, supplies
- Equipment – devices, software, temperature monitors
- Environment – site conditions, distractions, space
- Management – oversight, leadership, expectations
You list the problem at the “head of the fish”
Then brainstorm causes under each category.
🔍 Fishbone Example (Clinical Scenario) — expand
Problem:
Deviation: Visit performed outside the protocol window.
Let’s brainstorm the possible causes:
People
- Coordinator miscalculated the window
- Staff overloaded with multiple duties
Process
- No visit planning checklist
- No SOP for scheduling visits
Materials
- Manual paper calendar used
- No digital reminders
Equipment
- EDC calendar not used
- Scheduling software outdated
Environment
- Busy clinic leading to interruptions
- Frequent rescheduling of appointments
Management
- No oversight of upcoming visits
- PI not reviewing patient trackers
🎯 Root Cause after analysis:
Dependence on unreliable manual methods for scheduling visits.
✨ Solution:
Implement validated scheduling tools, staff training, and oversight checks.
🆚 5 Whys vs Fishbone: When to Use Each
Tool
Best for
Strengths
5 Whys
Simple problems with a direct cause
Fast, easy, reveals hidden reasons
Fishbone
Complex or multi-factor issues
Organized brainstorming, visual, thorough
Often both are used together:
Start with a Fishbone to brainstorm → Use 5 Whys to drill into the strongest cause.
⚙️ Why Every CRA Should Master These Tools
CRAs constantly encounter:
- protocol deviations
- consent issues
- missing data
- late reporting
- documentation errors
- IP temperature excursions
To prevent repeat issues, CRAs must be able to:
- ask strong RCA questions
- guide sites into deeper thinking
- help sites identify true root causes
- assess if CAPAs are realistic and effective
These tools help CRAs move from surface monitoring → to quality-driven oversight.
📘 Practical Tips for CRAs
- Don’t accept “human error” as a cause
- Encourage sites to avoid blame and focus on systems
- Use probing questions (“Walk me through your workflow…”)
- Make CAPAs specific, measurable, and assignable
- Revisit root causes during follow-up visits
📝 Mini Quiz — Test Your Knowledge
1.
The 5 Whys method is mainly used to:
2.
The Fishbone method is useful when:
3.
In the 5 Whys, asking “Why?” repeatedly helps:
4.
Which is not a Fishbone category?
5.
A CRA can use root cause analysis to:
List of Services
ABOUT THE AUTHOR
Mohamad-Ali Salloum, PharmD
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References: Quattash MS. The Depleted Mind: The Science of Decision Fatigue and Ego Depletion. Global Council for Behavioral Science. 2025. Available from: https://gc-bs.org/articles/the-depleted-mind-the-science-of-decision-fatigue-and-ego-depletion/ 5 Choudhury NA, Saravanan P. An integrative review on the causes and effects of decision fatigue. Front Cognit. 2026;4:1719312. Available from: https://www.frontiersin.org/journals/cognition/articles/10.3389/fcogn.2025.1719312/full 4 Schweitzer DR, Baumeister RF, Laakso EL, Ting J. Self-control, limited willpower and decision fatigue in healthcare settings. Intern Med J. 2023. Available from: https://onlinelibrary.wiley.com/doi/pdf/10.1111/imj.16121 3 Ordali E, Pietrini P. Mental fatigue leads to loss of self-control and poor decision-making. Coverage in The Brighter Side of News. 2024. Available from: https://www.thebrighterside.news/post/mental-fatigue-leads-to-loss-of-self-control-and-poor-decision-making/ 2 Woodley BioReg. Decision Fatigue and Cognitive Load: A Scientific Perspective. Woodley BioReg. 2026. Available from: https://www.woodleybioreg.com/decision-fatigue-and-cognitive-load-a-scientific-perspective/ 1 Keller AJ. Decision Fatigue: What It Is and How It Affects Your Brain. Neurosity Guide. 2026. Available from: https://neurosity.co/guides/decision-fatigue-brain
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