Six Sigma: pros, cons and when you need something else
Six Sigma removes variation from a process. Clearahead removes what’s holding a goal back. Related ideas, different jobs
The short answer
Six Sigma is a data-driven method for cutting defects and variation in repeatable processes, using DMAIC and trained Belts. Clearahead is software for a company goal: it finds the constraints holding the goal back and tracks the moves that clear them, with AI keeping it current. They come from the same family of ideas as the Theory of Constraints, but they do different jobs. Use Six Sigma to make a process reliable; use Clearahead to keep the whole company focused on what’s in the way of the goal.
What is Six Sigma?
Six Sigma is a set of methods for improving processes by finding and removing the causes of defects and variation. The name comes from statistics: a process running at six sigma produces about 3.4 defects per million opportunities. In practice, few organisations aim for that everywhere; the point is to measure how a process performs and make it reliably better.
Most Six Sigma work follows DMAIC: Define the problem, Measure the current process, Analyse the causes, Improve it, and Control it so the gains stick. New processes use a variant called DMADV. The work is led by trained people with martial-arts style titles: Champions sponsor projects, Master Black Belts coach, Black Belts lead projects full time and Green Belts take part alongside their day jobs. Many organisations now combine it with Lean, which focuses on flow and waste, as Lean Six Sigma.
Where Six Sigma came from
Bill Smith, an engineer at Motorola, introduced Six Sigma in 1986, building on decades of quality work by people like W. Edwards Deming and Joseph Juran. Motorola went on to register Six Sigma as a trademark. The method became famous in 1995, when Jack Welch made it central to how GE was run, and from there it spread across manufacturing, healthcare, financial services and beyond.
It has had its critics. Juran himself called it a basic version of quality improvement with nothing new in it, others questioned its statistics, and studies have found many projects fail to deliver. But in the right setting, a stable process with plenty of data, it works, and the habit of measuring before deciding is worth having anywhere. We've written about how the systems of the 1980s and 1990s fit into the longer story in Why are you doing that?
Six Sigma pros and cons
What Six Sigma does well, and where it struggles.
Where Six Sigma shines
- It’s rigorous. Decisions rest on measurement and statistics, not opinion.
- DMAIC gives teams a clear, repeatable way to attack a problem.
- It has a long record in manufacturing, healthcare, finance and logistics.
- The Belt system builds real skills and gives people a career path in improvement.
- Combined with Lean, it tackles waste and flow as well as variation.
Where Six Sigma struggles
- It’s heavy. Projects can take months, and training and certification take time and money.
- It suits stable, repeatable processes far better than new products or fast-changing markets.
- It can turn into a programme of projects that improve things that weren’t holding the business back.
- Critics, including quality pioneers like Joseph Juran, have argued it adds little that’s new.
- It’s built for specialists rather than the whole company.
Six Sigma vs Clearahead: side by side
| Six Sigma | Clearahead | |
|---|---|---|
| What it is | A method for reducing defects and variation in processes | Software for one company goal: the constraints holding it back and the moves that clear them |
| Where it comes from | Bill Smith at Motorola, 1986; made famous by GE from 1995 | The Theory of Constraints, rebuilt for teams that work with AI |
| The question it answers | Why is this process producing defects, and how do we fix it? | What is holding the goal back, and who is clearing it? |
| How work is organised | Improvement projects run through DMAIC or DMADV | Moves, each with one owner and a due date, under the constraint they clear |
| Who does it | Trained Champions, Black Belts and Green Belts | Everyone: leaders own constraints, their teams own moves, advisers follow as Viewers |
| Measures | Statistical: defects per million opportunities, sigma level, capability | How you’ll know the goal is met, plus evidence on every constraint and move |
| Best fit | Stable, high-volume processes | Hard company goals with no obvious path |
| Cost | Training, certification and project time; the method itself is public | Free for up to 3 people and 1 workspace; £297/month or £2,997/year for the whole company |
How Six Sigma and Clearahead differ in practice
Six Sigma and Clearahead share some ancestry. Both owe a lot to the quality movement and to the idea, made famous by Eliyahu Goldratt's Theory of Constraints, that improving the wrong thing is wasted effort. Where they differ is the scale they work at.
A process, or a goal
Six Sigma zooms in on a process and makes it reliable. Clearahead zooms out to a company goal, such as doubling revenue or launching in a new market, and asks what is really holding it back. Sometimes the answer is a process problem, and a Six Sigma project is exactly the right move. Often it's something else entirely: a missing hire, a pricing question, a decision nobody has made.
Specialists, or everyone
Six Sigma relies on trained Belts. Clearahead is built for the whole company: heads of department own constraints, their teams own moves, and the board and advisers follow along as Viewers. Nobody needs a certificate; they talk to AJ, the AI inside Clearahead, which updates the model and logs the evidence.
Projects, or a loop
A Six Sigma project runs from Define to Control, often over months. Clearahead runs as a loop: set the goal, find what's holding it back, move on it, and when it clears, find the next thing. AJ's weekly brief flags up to three things that need a decision, so the loop keeps turning without a review meeting.
What Clearahead doesn't do
Clearahead has no statistical tools, control charts, process maps or capability analysis. It won't tell you your sigma level. If your problem is variation in a process, you need Six Sigma or Lean tools, not us.
Should you choose Six Sigma or Clearahead?
Choose Six Sigma if
- You have a repeatable process, such as manufacturing, claims or fulfilment, with too many errors.
- Quality and consistency are what your customers are paying for.
- You have the data, the volume and the people to run statistical improvement projects.
- You’re in a regulated industry where documented process control matters.
Choose Clearahead if
- Your challenge is a company goal, like growth, a launch or a turnaround, not a single process.
- You need to find the constraint before you know which process to improve.
- You want the whole team involved, not just trained specialists.
- You move too fast for months-long improvement projects.
Our honest read
Six Sigma is the right tool when you know which process is the problem and you need to fix it properly. It is the wrong tool for figuring out what the company should focus on, and it's heavy for a small team moving fast.
Clearahead is for the step before: finding the constraint on the goal and getting everyone moving on it. If that constraint turns out to be a process, bring in the rigour. Lean's war on waste and Goldratt's focus on one constraint at a time are timeless principles; what dates is the ritual around them, which is why we built Clearahead to remove constraints rather than add initiatives.
Questions about Six Sigma
How does Six Sigma relate to the Theory of Constraints?
They’re cousins. The Theory of Constraints says to find the one thing limiting the whole system and focus there. Six Sigma and Lean are often used to fix that constraint once it’s found. Clearahead applies constraint thinking to a company goal, not a production line.
Can you use Six Sigma and Clearahead together?
Yes. If one of your constraints turns out to be a process problem, such as error rates in onboarding, a Six Sigma project can be a move under that constraint in Clearahead, with its owner, due date and evidence.
Is Six Sigma still relevant?
Yes, where processes are stable and high-volume. It is less suited to new products or fast-changing markets, which is where many smaller and AI-native companies spend most of their time.
Do I need training to use Clearahead?
No. AJ walks you through setting your first goal in a conversation, and the docs and videos cover the rest.