Nominal Group Technique and Its Use in Six Sigma

In Six Sigma projects, effective decision-making is essential. Teams often need to solve complex problems, define customer requirements, or prioritize root causes. In these situations, the Nominal Group Technique (NGT) offers a structured and inclusive way to gather ideas and rank them based on group consensus.

This article explains what NGT is, how it works, and why it’s useful in Six Sigma. You’ll learn when to use it, how to facilitate it step by step, and how it compares to other brainstorming techniques. You’ll also see real-world examples and tables to illustrate each concept.

What Is Nominal Group Technique?

Nominal Group Technique is a structured group brainstorming method. It helps teams generate ideas, clarify them, and prioritize them through a democratic voting process. NGT ensures every participant has an equal opportunity to contribute. It prevents domination by a few vocal individuals and avoids groupthink.

Although it involves a group, the term “nominal” means that the team works individually at first, before sharing ideas with the group. This structure leads to high-quality input and focused decision-making.

Why Use NGT in Six Sigma?

Six Sigma focuses on data-driven decisions and team collaboration. However, not all decisions can be made using hard data alone. In many cases, especially in the Define, Measure, and Analyze phases of DMAIC, you need subjective input from cross-functional teams.

Here’s why NGT works so well in Six Sigma:

Benefit	Explanation
Equal participation	Every team member contributes ideas individually.
Structured collaboration	The process follows a defined structure that promotes focus and clarity.
Prioritized outcomes	Ideas are not just listed—they are ranked by the group.
Reduced bias	Dominant personalities can’t overshadow others.
Efficient decision-making	Discussions remain goal-focused and time-bound.
Support for root cause analysis	NGT helps identify and prioritize potential root causes quickly.

NGT complements Six Sigma’s emphasis on team involvement and systematic problem-solving.

When Should You Use NGT in Six Sigma?

You should use NGT when your team needs to:

• Identify key problems from multiple perspectives
• Prioritize a long list of potential causes or solutions
• Achieve quick consensus from a diverse group
• Prevent one person from dominating a group decision
• Encourage equal input from all team members

Common Six Sigma Applications

Six Sigma Phase	How NGT Helps
Define	Identify customer needs (Voice of the Customer)
Measure	Select process metrics or data collection priorities
Analyze	Prioritize root causes identified in cause-and-effect diagrams
Improve	Rank improvement ideas or solutions
Control	Choose control methods or monitoring plans

NGT supports many Six Sigma tools like Fishbone diagrams, FMEA, CTQ Trees, and Project Charters.

Steps to Facilitate the Nominal Group Technique

Facilitating NGT requires following a specific, five-step process. Each step contributes to unbiased input and collaborative decision-making.

Step 1: State the Problem or Question Clearly

Start by identifying a clear, focused question. The facilitator writes it where everyone can see it. The question must be specific enough to guide idea generation.

Examples:

• “What are the main reasons for customer complaints about product X?”
• “What are the biggest delays in our shipping process?”
• “Which training gaps most affect operator performance?”

Avoid vague or multi-part questions. Clarity sets the stage for better ideas.

Step 2: Silent Idea Generation

Give each participant 5–10 minutes to silently write down as many ideas as they can. They should work individually, without talking or sharing yet. Encourage them to write one idea per sticky note or line on a sheet.

This step ensures:

• No early influence from others
• Equal thinking time for everyone
• Rich, unbiased input

Step 3: Round-Robin Idea Sharing

Next, go around the room and ask each person to share one idea at a time. The facilitator writes the ideas on a whiteboard or flipchart. Keep cycling through the group until all ideas are shared.

Important rules:

• No evaluation or discussion yet
• Only share one idea per turn
• Don’t skip people—include everyone

This format makes sure that quieter participants are heard and avoids duplicate discussions.

Step 4: Clarify and Discuss the Ideas

Once all ideas are listed, the group begins a discussion to clarify what each idea means. The goal is to:

• Merge duplicates
• Explain unclear ideas
• Group similar ideas into categories

Still, no judgment or ranking happens during this step.

This discussion ensures the group shares a common understanding of what each idea means before voting.

Step 5: Vote and Rank the Ideas

Each participant selects their top 5 ideas based on importance or relevance. They assign points to each ranked idea.

A common point system:

Rank	Points
1st	5
2nd	4
3rd	3
4th	2
5th	1

After everyone votes, the facilitator collects and totals the points. The ideas with the highest scores become the group’s top priorities.

You can also display results as a bar graph or Pareto chart for visual clarity.

Detailed Example: Using NGT in the Analyze Phase

Let’s say a Six Sigma team is trying to reduce scrap rates in a battery manufacturing process. They want to find and prioritize the most likely causes.

Problem Statement

“What are the main causes of scrap in the cathode coating line?”

Team Members

• Process engineer
• Quality technician
• Maintenance supervisor
• Production line lead
• Materials specialist
• Operator

Step-by-Step NGT Session

Step 1: Silent Idea Generation

Each member writes down their own ideas:

• Incorrect slurry mix
• Blade misalignment
• Dirty coating rollers
• Operator errors
• Poor lighting
• Uncalibrated sensors
• Material contamination

Step 2: Round-Robin Sharing

Ideas are listed as follows:

1. Incorrect slurry mix
2. Blade misalignment
3. Dirty rollers
4. Operator errors
5. Poor lighting
6. Sensor drift
7. Contaminated materials
8. Drying oven malfunction

Step 3: Clarification

The group decides to group some items:

• “Dirty rollers” and “contaminated materials” become “foreign material contamination.”
• “Sensor drift” and “uncalibrated sensors” become “sensor calibration issues.”

Revised list:

1. Incorrect slurry mix
2. Blade misalignment
3. Foreign material contamination
4. Operator errors
5. Poor lighting
6. Sensor calibration issues
7. Drying oven malfunction

Step 4: Voting

Each member votes and assigns points:

Cause	Points
Foreign material contamination	23
Incorrect slurry mix	21
Sensor calibration issues	18
Operator errors	15
Blade misalignment	10
Drying oven malfunction	9
Poor lighting	6

Outcome

The team focuses root cause analysis on the top three causes. They perform deeper investigations like 5 Whys and statistical testing on those issues.

Comparison: NGT vs. Traditional Brainstorming

NGT offers several advantages over informal brainstorming sessions.

Feature	Nominal Group Technique	Traditional Brainstorming
Silent idea generation	Yes	No
Equal participation	High	Often unbalanced
Structured format	Yes	No
Risk of groupthink	Low	High
Prioritization included	Yes (voting)	Often missing
Best for cross-functional teams	Yes	Sometimes

If your Six Sigma team includes a mix of roles and personalities, NGT creates a level playing field.

Combining NGT with Other Six Sigma Tools

NGT works even better when paired with other Six Sigma techniques.

Six Sigma Tool	How NGT Enhances It
Fishbone Diagram	Helps identify and prioritize root causes
FMEA	Helps rate severity, occurrence, and detection
Project Charter	Clarifies key goals and stakeholder concerns
CTQ Tree	Prioritizes critical customer needs
Control Plan	Identifies the most important control steps

Use NGT early in the project to shape the scope and later to validate improvement ideas.

Best Practices for Facilitating NGT

Follow these tips to make your NGT sessions more effective:

• Use an experienced facilitator: This person should remain neutral and ensure fairness.
• Define roles: Assign a timekeeper and note taker if needed.
• Stick to the structure: Don’t rush or skip steps.
• Use visuals: Write ideas where everyone can see them—on sticky notes, whiteboards, or screens.
• Encourage creativity: Remind the team there are no wrong answers during idea generation.

Pitfalls to Avoid

Avoid these common mistakes during NGT sessions:

Mistake	Problem It Causes
Vague question	Results in unfocused or scattered ideas
Skipping the silent phase	Leads to biased or shallow input
Allowing early discussion	Encourages groupthink
Letting strong personalities dominate	Undermines group fairness
Not documenting votes	Makes it hard to track and act on results

A well-executed NGT session creates trust and alignment.

Real-World Example: Reducing Customer Returns

A Six Sigma team at an electronics manufacturer used NGT during a project to reduce returns.

Problem Statement

“What are the top reasons customers return smartwatches within 30 days?”

Participants

• Customer service lead
• Quality manager
• Design engineer
• Repair technician
• Sales rep

Outcome of NGT

Top-ranked reasons:

1. Screen scratches easily
2. Battery life disappoints users
3. Confusing setup instructions
4. App crashes on Android phones

The team used these insights to redesign packaging, update onboarding instructions, and fix app bugs. Return rates dropped 22% in the next quarter.

Conclusion

The Nominal Group Technique is a powerful tool for Six Sigma teams. It encourages equal participation, avoids groupthink, and helps prioritize the most important ideas. Whether you’re identifying customer needs, ranking failure modes, or narrowing down root causes, NGT adds structure to your decision-making process.

By using NGT in your Six Sigma projects, you create more inclusive, data-informed, and effective outcomes.