An introduction to Lean Six Sigma

Better work starts with understanding what customers need and helping the people doing the work improve how it gets done. Lean Six Sigma brings a structured, evidence-based approach to that challenge.

This guide explains why continuous improvement matters, how Lean removes waste, how Six Sigma reduces variation and defects, and how the Define, Measure, Analyze, Improve, Control (DMAIC) method turns a problem into a sustained improvement.

Make improvement part of everyday work

Engaged, accountable people

Empower employees to suggest solutions and lead their implementation. Improvement becomes a shared responsibility.

A shared way of working

Establish standards, best practices, and procedures so teams speak the same language.

More capacity

Efficient processes free up time, people, and resources for new opportunities.

Stronger customer value

A deeper understanding of customer needs helps teams improve their offerings and compete more effectively.

Greater readiness for change

Regular improvement helps people become more open to new ideas and ways of working.

Better customer service

Understanding the customer builds empathy and gives employees a clearer reason to deliver on customer needs.

The customer defines value. Lean focuses on removing unnecessary steps that do not contribute to that value. Progress shows up in smoother flow, shorter cycle times, and lower variable costs.

Start by separating work that creates customer value from work that is necessary for the business and work that can be removed. Some non-value-adding activities, such as required controls, still need to happen; improve them without compromising their purpose.

These percentages illustrate an opportunity to improve; they are not a benchmark for every process. The goal is an increasingly direct path from customer need to valuable output, with less waste and fewer unnecessary resources.

The eight types of waste

The Japanese term muda describes waste. Look for all eight forms, including the waste of people’s knowledge and ability.

Unused talent

Underusing people’s skills, assigning avoidable non-value-adding work, or ignoring frontline feedback.

Overproduction

Producing earlier or in greater quantities than the next step or customer needs.

Transportation

Moving materials or work unnecessarily between places or teams.

Motion

Unnecessary movement within a work process.

Overprocessing

Doing more processing than the customer needs or values.

Waiting

Spending time waiting rather than adding value.

Inventory

Holding more finished goods, work in progress, or raw materials than needed to meet immediate demand.

Defects

Using time, effort, and materials to fix errors or redo work.

What better flow looks like

Review six commonly overused resources: equipment, space, labor, time, complexity, and materials. The aim is to use what is needed to deliver value, not to remove capacity or controls indiscriminately. Less waste means smoother flow, fewer resources consumed, and a more predictable process.

Customers define quality through their needs and expectations. Translate those expectations into measurable requirements. A defect is a failure to meet a requirement; those failures can cause customer dissatisfaction.

Six Sigma focuses on the relationship between a process’s inputs (the Xs) and its output (the Y). Understand and improve the inputs that influence the result, then measure changes in defects and variation.

In the presentation’s pizza example, suppliers provide ingredients, the kitchen prepares and cooks them, and the finished pizza goes to the customer. Improving the output means understanding the inputs and preparation process, not simply checking the pizza at the end.

Not all variation means a process is out of control

Common-cause variation is the ordinary variation inherent in the current process. A stable process still varies. Reducing that variation usually requires changes to the system itself.

Special-cause variation comes from an identifiable change or unusual event affecting the process. Investigate shifts, trends, and other signals before deciding what action to take. These causes may arise within or outside the process.

A controlled process behaves consistently over time. An uncontrolled process may have shifting averages or changing spread. Stability and meeting customer requirements are different questions: a stable process can still consistently deliver the wrong result. See NIST’s explanation of controlled and uncontrolled variation.

Standard deviation (σ) describes the spread of measurements around their mean. Sigma capability relates that spread and the process’s position to specification limits. Higher capability generally means fewer outputs outside the customer’s requirements.

Defects per million opportunities (DPMO) expresses defects relative to the number of opportunities for a defect: defects ÷ total opportunities × 1,000,000. Define an opportunity consistently before comparing processes.

These conventional approximate rates use the Six Sigma assumption of a 1.5-standard-deviation shift. They are not the probabilities for a perfectly centered normal distribution at ±6σ. ASQ explains the convention.

Center the process and reduce its spread

The lower specification limit (LSL) and upper specification limit (USL) define acceptable outputs. These customer requirements are not the same as statistical control limits. A process can miss the target, vary too widely, or do both.

The presentation contrasts a manufacturer’s door-to-door view with a healthcare customer’s wing-to-wing view. A product leaving the factory is only part of the outcome; the customer cares about how it works across their operation. Consistent output, predictable processes, fewer defects, and less rework should support that broader definition of success.

A Cyber Monday thought experiment

Amazon reported more than 36.8 million items ordered worldwide on Cyber Monday 2013. The original training uses that scale to illustrate how small differences in defect rates can add up.

For this exercise, assume exactly 36.8 million opportunities, one opportunity per item, and a hypothetical $35 per error. Expected defects equal opportunities × DPMO ÷ 1,000,000; expected cost equals that result × $35.

Scroll sideways to see the full table.

At 5σ, the model produces about 8,574 errors and $300,104 in cost. At 6σ, it produces about 125 errors and $4,379. These are hypothetical outcomes, not Amazon’s measured error rates or costs.

Original example: The Council for Six Sigma Certification, 2018, as cited in the presentation. The web table recalculates every row from the displayed DPMO; defects and costs are rounded independently after calculation. “Items” corrects the original slide’s “orders” wording.

Why consistent results matter at scale

The presentation also uses the following comparisons, credited to Kyocera Document Solutions Europe, to make the effect of small error rates tangible.

Scroll sideways to see the full table.

These are legacy teaching illustrations, not observed safety, medical, or financial statistics. The source does not give the activity volumes or calculation assumptions, and the rows cannot be independently reconciled. Use the explicit formula above for calculations, not these illustrative counts.

Choose a method that fits the work. Improving an existing process is a different challenge from designing a new product, service, or operating process.

DMAIC

Define, Measure, Analyze, Improve, Control. Use it to improve an existing process and reduce defects.

Design for Six Sigma (DFSS)

A family of approaches for new designs or substantial redesigns. Build in customer requirements and defect prevention from the start.

DMADV

Define, Measure, Analyze, Design, Verify. One framework within DFSS, rather than a synonym for every DFSS approach.

IDOV

Identify, Design, Optimize, Verify. Another design framework, beginning with a clear understanding of customer needs.

The DFSS distinction is clarified using ASQ’s Design for Six Sigma guidance. The web edition expands the acronyms used in the original slides.

Work through DMAIC

Define the outcome and measure the baseline

The desired output, Y, is on-time delivery. In this exercise, the customer’s acceptable delivery window runs from 5 to 15 minutes, with a 7-minute target.

The presentation gives a baseline of approximately 57% on time and a mean delivery time of 20 minutes. The simple average of the seven daily percentages is about 57%; delivery counts would be needed to calculate a properly weighted overall rate. A mean time of 20 minutes is a separate supplied assumption, not something this table can establish.

Analyze the inputs

Map the delivery process and investigate the driver, freight type, load type, load size, distance, travel, time, and route. The exercise identifies route variation as the root cause and sets a target of 95% on-time delivery.

Improve through experiments

The slides propose testing routes with right turns only, left turns only, removing routes, or removing contracts. Treat these as hypotheses in the fictional exercise. Compare outcomes and customer impact before selecting a change; none is a prescribed solution.

Control the result

Monitor the selected solution, watch the variation, and confirm that the process continues to meet the requirement. The example shows how an output measure leads to investigation of inputs, tested changes, and ongoing control.

A Lean Six Sigma project is an investigative process. Discovery often takes the most time: resist jumping to a solution before understanding the problem and the evidence.

Lean Six Sigma is a way to understand customer needs, solve problems, make decisions with data, help others succeed, and identify opportunities methodically. It is not a cure for every problem, a replacement for engineering or process expertise, or simply a collection of tools.

Home Depot: efficiency and the customer experience

The deck describes a shift toward cost reduction around 2000: streamlined operations, automated inventory, centralized supply orders in Atlanta, and replacement of experienced staff with part-time help.

It reports revenue rising from $45.74 billion to $81.51 billion over five years and after-tax earnings from $2.58 billion to $5.84 billion, alongside lower morale, negative customer sentiment, a stock-price decline from $65 to $21 over three years, and a fall from the top to the bottom of a retail ranking that is not identified. The lesson is to assess the customer and employee experience alongside financial efficiency.

3M: protect the conditions for innovation

The presentation describes a response to slow growth and profitability in the late 1990s: a broad Six Sigma approach in research and development, a workforce reduction of 8,000, fewer production defects, more focused R&D resources, and rigorous performance reviews.

The deck reports revenue up 11%, net income up 21.7%, and stock price up 38%. It also describes employee dissatisfaction, harm to the innovation culture, and an 8% reduction in new products. Its caution is to fit the method to the work rather than impose uniform controls on every activity.

Lockheed Martin: connect improvement to sustainability

The deck describes a 1990s emphasis on sustainability: embedding goals in the culture, choosing environmental and performance measures, building alternative-energy partnerships, and expanding waste-disposal options.

Reported results are $95 million in savings, less physical space used, 12% lower energy dependence, a 20% cost reduction, 20% reductions in water use and carbon emissions, and 36% less landfill material. The example connects improvement measures to an explicit organizational purpose.

GE: make customer success a leadership priority

The presentation describes Jack Welch’s 1995 introduction of Six Sigma as part of how GE operated, with a goal of becoming a Six Sigma company by 2000. It highlights executive involvement, data-based problem solving, Black Belt training, annual retraining, and mentorship.

The deck reports 98% fewer billing and invoicing issues, $1 million in annual contract-review savings, an 85% reduction in hospital imaging time, a 27% improvement in customer-service response times, and improved responsiveness to regulators. The teaching point is that leadership, capability, and customer outcomes need to reinforce one another.

1. Define the real problem. Understand customer needs, their environment, and their goals before designing a solution.
2. Use a proportionate method. Kaizen and Lean can deliver quick wins where the problem and solution are already understood. Not every change needs a full Six Sigma project.
3. Address risks early. Identify bottlenecks and risks before they expand the scope or timeline.
4. Share the benefits early. Involve stakeholders and make the value visible to support participation and adoption.
5. Watch performance. Use a dashboard to spot unexpected variation and respond.
6. Listen after implementation. Gather voice-of-the-customer (VOC) feedback from people using the output.
7. Assign a process owner. Someone needs to monitor performance and sustain control after the project closes.
8. Keep improving. Make learning and improvement part of how the organization works.

Both start with the customer. Use them together to improve how work flows and how consistently it delivers the result people need.

Adapted from Anastasia Abuya’s 31-page Intro to Lean Six Sigma presentation. The web edition retains its substantive lessons and examples, reorganizes the material, and clarifies technical wording and calculations. The original PDF remains available unchanged.

• NIST/SEMATECH e-Handbook: controlled and uncontrolled variation, used to clarify process stability.
• ASQ: Six Sigma, supporting terminology and the distinction between waste and variation.
• ASQ: The Confusion Over Six-Sigma Quality, explaining the 1.5σ-shift convention.
• ASQ: Design for Six Sigma, clarifying the relationship between DFSS and DMADV.
• Amazon’s December 2013 holiday announcement, verifying the scale and unit of the Cyber Monday example. The hypothetical cost example was credited in the slides to The Council for Six Sigma Certification (2018).
• Kyocera Document Solutions Europe, “Introduction to Lean Six Sigma Methodology,” credited by the original presentation for the everyday consistency comparisons.
• Original illustration credits: HRB Family Business Consulting (slide 2) and VectorStock, image IDs 7595511, 20532180, and 1110536 (slide 20). Those illustrations are not reproduced here; web diagrams convey the underlying concepts.