Conquer Process Improvement With These 9 Lean Six Sigma Tools

Lean management, Six Sigma, and Lean Six Sigma all walk into a bar. Lean orders a Scotch. Six Sigma orders bourbon. Lean Six Sigma orders a hot toddy. The bartender says, “So that will be a whisky, a whiskey, and a bit of both.”

The joke works because the methods are related, but they are not identical. Lean removes waste, Six Sigma reduces defects and variation, and Lean Six Sigma combines both goals. This guide maps nine practical Six Sigma tools and techniques to the Define, Measure, Analyze, Improve, and Control stages of the DMAIC framework.

You do not need to use every tool on every project. Choose the lightest method that resolves the uncertainty in front of you: map the process, identify risk, prioritize the vital few, distinguish common from special causes, test root-cause hypotheses, improve the workplace, or hold gains with a control plan.

• Lean: Reduce or eliminate activity that does not add value to a process. Learn the core Lean principles.
• Six Sigma: Reduce defects and variation through evidence-based process improvement. Review the Six Sigma principles.
• Lean Six Sigma: Combine waste reduction with variation control inside the DMAIC process.

DMAIC stage	Question	Tools in this guide
Define	What problem and process are we improving?	Process flow chart, FMEA
Measure	What does the data show?	Pareto chart, SPC
Analyze	What could be causing the problem?	5 Whys, Fishbone diagram
Improve	How do we make and sustain a better way of working?	5S, Kaizen
Control	How do we keep the gains?	Control plan

How to choose the right tool: Start with the decision you need to make, not the diagram you want to draw. If people disagree about how work happens, map the process. If the process is known but the consequences of failure are uncertain, use FMEA. If you have defect or complaint data and need to prioritize, build a Pareto chart. If performance changes over time and you need to separate signal from noise, use a control chart.

Root-cause tools serve a different purpose. Use 5 Whys when a clear causal chain can be tested with evidence. Use a fishbone diagram when the team needs to organize several plausible causes before validating them. Neither method proves a root cause by itself. The investigation still needs observations, records, interviews, or experiments that can confirm or reject each hypothesis.

Once the cause is understood, choose an improvement method that fits the operating environment. 5S is useful when disorder, searching, inconsistent placement, or weak workplace standards create friction. Kaizen is broader: it creates a habit of small, repeated experiments owned by the people doing the work. A control plan belongs at the end because an improvement without ownership, measurement, and a defined response can quietly drift back to the old state.

Some projects need several tools in sequence, but more documentation is not automatically better. A process map followed by one targeted measurement may resolve the issue. A higher-risk process may justify FMEA, data analysis, root-cause validation, a controlled pilot, and ongoing monitoring. Match the depth of the method to the consequence of getting the decision wrong, and record enough evidence that another person can understand the decision and its rationale.

Jump to a DMAIC stage:

• Six Sigma tools: Define
• Six Sigma tools: Measure
• Six Sigma tools: Analyze
• Six Sigma tools: Improve
• Six Sigma tools: Control
• Final thoughts and further reading

Six Sigma tools: Define

The Define stage establishes the problem, the process boundary, and the risks that matter. Start with a process flow chart to see the work, then use FMEA when you need a structured view of possible failures and effects.

1. Process flow chart

A process flow chart, also called a process map or flow diagram, shows the sequence of work, decisions, delays, and handoffs in a process. It is often the first process improvement tool to use because it gives everyone the same view of how work actually moves.

A useful process map can:

• Clarify the start, end, and boundaries of a process.
• Expose non-value-added activity, rework, queues, and unclear ownership.
• Make handoffs and decision points visible.
• Create a shared baseline for measuring improvement.

Keep the first version simple. Use an oval or rounded node for the start and end, rectangles for activities, diamonds for decisions, and arrows for flow. The symbols matter less than whether the map reflects real work. Tools such as draw.io can make a clean diagram, but a whiteboard is enough to discover the process.

Consider a content approval workflow. A writer submits a draft directly to an editor, who returns extensive corrections. The visible bottleneck is not the editor alone. The map reveals that the draft reaches the editor before a peer review or quality check.

Add a peer-review step, route rejected drafts back for revision, and send only the corrected version to the editor. The improved map makes the new handoff explicit and gives the team a process it can test. The value is not a prettier diagram. It is a clearer hypothesis about where the delay and rework originate.

ASQ includes flowcharts and process maps among the basic quality tools. Use the map to agree on the current state before changing it.

2. Failure mode and effects analysis (FMEA)

I’m not being dramatic when I say that performing a thorough FMEA can save lives. The FMEA process measures risk and can be used in a multitude of situations. The risk in question may be financial (as in the case of British Airways £100 million process failure) or the safety of your customers and employees. Either way, you need to know what potential process failures you face, and what the effects of those failures will be if they happen. Once you do that, you can decide which to prioritize and how to address them. In basic terms, failure modes are all the points where a thing can go wrong, and the effects analysis is what happens when that thing goes wrong. The first step is to identify credible failure modes with the people who know the process. ASQ’s The Quality Toolbox provides a practical reference for structuring the analysis. Once the team has listed the failure modes, define a consistent scoring scale and assess each one across the dimensions required by the FMEA method you follow. Common dimensions include:

• Severity: How serious is the effect if the failure occurs?
• Occurrence: How likely is the cause or failure to occur?
• Detection: How likely are current controls to detect the failure before the effect reaches the customer or process?

Traditional FMEA often multiplies those ratings to calculate a Risk Priority Number. RPN can help organize discussion, but it should not be treated as a universal decision rule. Different combinations can produce the same score while representing very different risks, and a severe hazard should not be ignored simply because another rating is low.

Use the prioritization method required by your industry or standard. Automotive AIAG/VDA practice, for example, uses Action Priority. Whatever method applies, record the reasoning, proposed action, owner, due date, and evidence that the action reduced the risk. Then reassess the ratings after the action rather than assuming completion equals effectiveness.

Conducting an FMEA can seem daunting, particularly if you’re looking at an entire system of processes rather than a single one. If the grid system makes your eyes glaze over, check out this free template that you can run every time you conduct the failure mode and effects analysis:

Six Sigma tools: Measure

Alright, kids, hold on to your hat: if you thought FMEA got complicated, just wait until we get to statistical process control (SPC). (I’m kidding, SPC only looks scary. I promise it won’t bite.) The next two tools will be used to gather all the necessary data about your processes and where your improvements should happen first. The Pareto chart is essentially your elementary school bar graph with a very slight twist, while the SPC method is a flowchart on steroids. One step at a time, though.

3. Pareto chart

In 1897, economist Vilfredo Pareto created a formula to represent the distribution of wealth, now known as the 80/20 rule. Pareto intended to highlight the disparity of wealth (20% of the population possess 80% of the wealth), but the 80/20 rule has transcended Pareto’s initial goal. In terms of business, the 80/20 rule means that a large share of the result comes from only 20% of the effort. Several decades after Vilfredo Pareto’s realization, engineer and management consultant Dr. Joseph M. Juran published his book, Quality Control Handbook, which outlined his three principles of quality management. The first principle? Pareto’s 80/20 rule, which eventually became the Pareto chart that we all know and love today. Organizations now use Pareto charts as a vital tool for root cause analysis and quality management. (The other two principles are management theory and the Juran trilogy, if you want to know more.) Juran realized that most defect distributions follow a pattern very similar to the 80/20 rule: a small number of issues creates the majority of defects. The Pareto chart, then, shows the relative frequency of defects in rank-order which allows you to prioritize improvements. Pareto charts tend to take the standard bar graph appearance and can be created with little effort using any spreadsheet or charting software. Below is an example of a basic Pareto chart I made in Microsoft Word to assess causes of customer churn. At a glance, you can see right off the bat that the primary reason customers have for canceling their accounts is the product’s price. With that in mind, you can examine your current strategies and consider the best option for reducing churn in the future. See? Simple. Now, you could stop there, or you could do something pretty amazing: you could add a line. Do not underestimate the humble yet esteemed line, dear reader; it’s more valuable than you think. Let me explain: For a basic Pareto chart, you will only use the standard X/Y format, and your bars will be organized from highest to lowest, left to right (as above). In the example, the Y-axis shows the frequency a cause occurs during the first quarter of the year, while the X-axis lists the individual causes. The line is for the Z-axis, or the cumulative percentage of all issues that can be removed if the most important ones are resolved. Getting the cumulative percentage will take a little bit of math, but it’s nothing too complicated. (Trust me: I am the worst at math.)

1. Add each sum together to get a grand total: 32 + 27 + 19 + 13 + 9 = 100
2. Get the percentage for each item by dividing the sum by the grand total:
• (32 / 100) x 100 = 32%
• (27 / 100) x 100 + a = 59%
• (19 / 100) x 100 + b = 78%
• (13 / 100) x 100 + c = 91%
• (9 / 100) x 100 + d = 100%
3. Chart a line on your graph by connecting the points for each percentage.
4. Once finished, your Pareto chart should look something like this:

Now, locate the 80% mark on the Z-axis and trace across until you intersect the cumulative percentage line (in red above). Drop a dotted line down from that point. The issues to the left of the dotted line are the “vital few of many” to focus on for the greatest effect. As I said, Pareto charts can be made using a variety of programs from the Microsoft suite to Creately, goleansixsigma’s template, our Pareto Chart checklist which takes you through creating one in Excel step-by-step.

4. Statistical process control (SPC)

SPC only looks scary. At its core, statistical process control uses time-ordered data to distinguish routine process variation from a signal that deserves investigation.

Walter A. Shewhart developed control charts at Bell Laboratories. W. Edwards Deming later expanded the use of statistical quality control and helped make variation central to process improvement. The method remains useful because reacting to every rise and fall can make a stable process worse.

A control chart usually contains:

• A time-ordered series of measurements.
• A center line representing the process average or another chart-specific statistic.
• Upper and lower control limits calculated from the process data.

Points and patterns inside those limits generally represent common-cause variation built into the current process. A point beyond a limit, a sustained shift, or another chart-specific rule can indicate special-cause variation. Investigate the signal before redesigning the whole process.

There is no universal minimum of 25 points or one four-rule set that applies to every chart. The right chart, subgrouping method, assumptions, and interpretation rules depend on the data and process. ASQ’s control chart guide and the NIST engineering handbook explain the core logic and chart selection.

Once special causes are understood and the process is stable enough to learn from, use an improvement cycle such as PDCA or PDSA to test changes. The control chart then helps show whether the improvement shifted the process or merely created another temporary fluctuation.

Six Sigma tools: Analyze

The next few tools are a little easier to use. At least, they don’t require any math to complete. Both the 5-Why analysis and the Fishbone diagram are actually used quite well in conjunction with each other, with the Fishbone diagram serving as a natural extension of the 5-Whys.

5. 5-Why analysis

If you’ve ever spent any length of time with a small child, you’ll be very familiar with this method. To perform the 5-Why analysis, you ask yourself “Why?” five times in succession. The goal behind this is to understand the root cause of the problem.

“For want of a nail the shoe was lost…” The familiar chain from Benjamin Franklin’s 1758 “The Way to Wealth” shows how a small cause can compound through a system. Read the primary text.

Franklin’s example, converted into a modern 5-Why analysis, would look something like this: The 5-Why analysis shows how a seemingly inconsequential issue can have wide-ranging, and incredibly serious consequences. It encourages teams to look beyond the simple defect at all possible causes, and treat the disease rather than the symptoms.

Five is a prompt, not a proof threshold. Stop when you reach an evidence-supported cause, which may take fewer or more questions, and validate the conclusion with process data before acting.

6. Fishbone diagram

A fishbone or Ishikawa diagram follows a similar process, but uses a visual approach to documenting the answers. The fishbone is made by creating a graphic that looks (shockingly )like a fish skeleton. This is primarily a team-based analysis that can be done on a whiteboard or in any shared diagramming surface. The steps themselves are easy:

1. Write the problem (or effect) on one side of the workspace and draw a “backbone” across the page.
2. Decide whether to categorize the causes by function (most common approach) or process sequence.
3. Once you have your initial categories, you need to list sub-categories, either through data collection or brainstorming. (This is a good stage to use the 5-Whys.)
4. Select the most plausible causes for validation, then use evidence to identify the root cause and create a response. The diagram organizes hypotheses; it does not prove them.

Six Sigma tools: Improve

After defining, measuring, and analyzing the problem, the Improve stage changes how work is done and makes the better method easier to sustain. 5S stabilizes the workplace, while kaizen keeps the process evolving through small, owned improvements.

7. 5S tool

5S references five Japanese words (all beginning with the letter “S”) that should govern workplace organization:

• Seiri
• Seiton
• Seiso
• Seketsu
• Shitsuke

Translated into English, the five concepts of the 5S tool are: Sort Separate necessary and unnecessary items, then remove all unnecessary ones.

• What’s the purpose of this item?
• How often is it used?
• Does it really need to be here?

Set in order Optimize your workstation so necessary items can be reached quickly and easily.

• Which items are used most frequently?
• Where is the best placement for the items?
• Is more storage needed to stay organized?

Shine Keep your workspace clean and organized. This reinforces process discipline and adherence by emphasizing that positive working conditions matter. Standardize Standardize your processes to prevent deviation normalization: create schedules, assign tasks, and set reminders so cleanliness and organization are maintained.

• What tasks need to be completed every day? Every week?
• Who should be responsible for each task?
• Are processes documented and optimized for adherence?

Sustain Keep the entire team involved in maintaining your processes so the changes are sustainable and become integrated into your organization’s culture.

• Are new employees taught the proper processes?
• Is the whole team holding each other accountable?
• Can the processes be improved in any way?

8. Kaizen

Kaizen is the practice of continuous improvement. The Lean Enterprise Institute describes it as ongoing improvement based on many small changes. Read the definition. With kaizen, every employee is encouraged to take ownership, identify improvement opportunities, and implement these changes on a continual basis. One of the ways we apply this at Process Street, is that every team member is encouraged to not only think about how we can perform processes more efficiently, but actively identify irrelevant tasks and think about how the process can be improved. Every time we complete a task or a workflow run, we ask ourselves: Is this step still beneficial to the process? Is there a more effective way we can accomplish the same goal? As a result, our processes are constantly evolving to meet our current needs, which means increased process adherence. After all, if the processes are working, there’s no reason not to follow them. By encouraging this consistent re-evaluation of established processes, kaizen ensures that your processes do continue to work for the people who use them most.

Six Sigma tools: Control

Personally, I don’t think control is the best word here, but no one asked me when they came up with the acronym. The final stage of DMAIC is where you make sure your new processes are running consistently and efficiently. Process documentation is the name of the game at this point; you want a clear, accessible plan outlining the changes that are being made, the order they’ll be made in, and who will be making them. That way you’re able to monitor the improvements to ensure they actually are improvements. Alternatively, you’ll also be able to see where the improvements aren’t.

9. Control plan

A control plan is the documented agreement for holding an improvement in place. It connects each critical process characteristic to an owner, a measurement method, a review frequency, acceptable limits, and a response when performance moves outside those limits.

A useful control plan answers:

• What must stay in control?
• Who owns the measure and the response?
• How and how often will the process be checked?
• What evidence proves the check happened?
• What action follows a missed limit or failed effectiveness review?

Keep it proportional to the risk. A simple process may need one short register. A regulated or safety-critical process may need linked procedures, approval records, evidence, escalation paths, and formal review cadence. ASQ distinguishes a quality or control plan from a decision matrix, which compares options rather than monitoring performance.

Process Street is a single Compliance Operations Platform with Docs and Ops capability areas plus built-in AI. Teams can govern the procedure in Docs, execute the control through auditable Ops workflows, and use built-in AI to flag missed steps, delays, and improvement opportunities. That keeps the control plan connected to the work instead of leaving it in a static spreadsheet.

Final thoughts and further reading

These are still my personal favorites among Lean Six Sigma tools. I do not enjoy solving equations, but I do enjoy a good diagram, which makes the effort worthwhile.

Visual methods make it easier to explain how work flows, where variation or waste enters the process, and what needs to change. The important part is not the diagram alone. Document the decision, test the improvement, assign ownership, and keep evidence that the new process works.

If you need adjacent methods, explore these quality management tools and the following guides:

• How to Solve Your Problems With Lean Six Sigma
• Gap Analysis: How to Bridge the Gap Between Performance and Potential
• What is Process Mining? 9 Tools to Optimize Your Process Management

What is your favorite Lean Six Sigma tool? Did I leave out one that deserves more attention?

The post Conquer Process Improvement With These 9 Lean Six Sigma Tools first appeared on Process Street | Compliance Operations Platform.