The 6 Ms of a Fishbone Diagram, Explained
- timothyferguson1
- Jun 13
- 3 min read
June 13, 2026
When you build a fishbone diagram, each “bone” is a category of causes — and choosing good categories is what stops a team from fixating on one area and missing the rest. The most widely used set is the 6 Ms. This post explains what each one covers, gives you prompting questions, and shows where the variants (5M1E, the 4 Ss, and HOP) fit.
New to fishbones? Start with How to make a fishbone (Ishikawa) diagram. https://www.fsquaredconsultinggroup.com/post/how-to-make-a-fishbone-ishikawa-diagram-step-by-step
Why use categories at all?
Left to free-associate, teams pile causes into whatever area they know best — usually “people.” Categories act as prompts that force you to look everywhere: at the process, the equipment, the materials, the environment, and the management system, not just the operator. That breadth is the entire value of a fishbone.
The 6 Ms
1. People (Manpower)
The human element: skills, training, experience, staffing levels, fatigue, communication, and clarity of roles. Ask: Are people trained for this task? Is the workload sustainable? Are responsibilities clear? Examples: new operators undertrained, shift-handoff gaps, unclear ownership.
2. Process (Methods)
How the work is actually done: procedures, sequence, standards, handoffs, and checkpoints. Ask: Is there a standard? Is it followed? Are there missing checks or too many handoffs? Examples: no standard changeover procedure, missing inspection step, rework loops.
3. Equipment (Machines)
The tools and machinery: condition, maintenance, calibration, capability, downtime, and tooling. Ask: Is equipment maintained and calibrated? Is it capable of the spec? Does it flag problems? Examples: sealer temperature drift, worn blades, no error detection.
4. Materials
The inputs: raw material quality, consistency, specification, supplier variation, storage, and shelf life. Ask: Are materials in spec and consistent batch to batch? Stored correctly? Examples: film thickness varies by lot, adhesive past shelf life, wrong spec received.
5. Environment
The conditions the work happens in: temperature, humidity, lighting, noise, layout, cleanliness, and space. Ask: Could conditions affect the process or the people? Does it vary by shift or season? Examples: high humidity on the night shift, poor lighting, cluttered workspace.
6. Management
The system around the work: priorities, resourcing, policies, decision-making, and how quality is supported. Ask: Do priorities or incentives drive the behavior? Is there support and follow-up? Examples: throughput prioritized over quality, inadequate budget, no follow-up on issues.
A worked example across the 6 Ms
Problem: ~6% of Line 3 cartons ship with unsealed top flaps.
• People: new operators undertrained on changeover
• Process: no standard changeover procedure
• Equipment: sealer temperature drifts after changeover
• Materials: carton film thickness varies by lot
• Environment: high humidity on the night shift
• Management: throughput prioritized over quality checks
Filling every category surfaces candidates a “people-only” view would miss — here, the process and equipment branches turned out to matter most.
Variants you’ll encounter
• 5M1E — People, Methods, Machines, Materials, Measurement, and Environment. Adds Measurement (is the gauge/inspection itself reliable?) — useful in precision and metrology contexts.
• The 4 Ss — Surroundings, Suppliers, Systems, Skills — common in service industries where “machines and materials” fit awkwardly.
• HOP / Human & Organizational Performance — categories like Task Demands, Work Environment, Individual Capabilities, Human Nature, Organizational Factors, and Leadership — used in safety and human-performance work to examine why people did what made sense to them, without blame.
Pick the set that fits your work. The goal is comprehensive prompts, not loyalty to a particular acronym.
Build it free: The F Squared fishbone tool comes with 6M and HOP category sets built in (and you can rename categories to fit your process). Try it free →
Prefer paper? The free RCA Starter Kit includes a printable 6M fishbone template. https://www.fsquaredconsultinggroup.com/digitaltools
Frequently asked questions
What are the 6 Ms of a fishbone diagram?
People (Manpower), Process (Methods), Equipment (Machines), Materials, Environment, and Management — the classic categories for organizing the possible causes of a problem.
What’s the difference between the 6 Ms and 5M1E?
5M1E uses People, Methods, Machines, Materials, Measurement, and Environment — it swaps “Management” for “Measurement,” which is handy when gauge or inspection reliability is in question.
Do I have to use all six categories?
Use the ones that fit your problem, but resist dropping a category just because it feels empty — the quiet categories are often where overlooked causes hide.
What categories should service teams use?
Many use the 4 Ss (Surroundings, Suppliers, Systems, Skills) or a HOP set instead of the manufacturing-flavored 6 Ms. Choose prompts that match your work.
What comes after categorizing causes?
Pick the most likely cause(s) and run a 5 Whys to confirm the root, then document it in an A3. Fishbone vs 5 Whys vs A3. https://www.fsquaredconsultinggroup.com/post/fishbone-vs-5-whys-vs-a3-when-to-use-each