Mulbury Six Sigma

Six Sigma quality explained in 10 easy points...

One

Everything we do is a process

Business processes usually perform an action on the main entity passing through the process, to physically change it and add value in the eyes of the customer.

Manufacturers use processes to add value to products, and service industries use processes to deliver value-added services.

Two

Every process has measurable characteristics

The process itself will have requirements for the inputs, and the customers will have requirements of the outputs. Even if we are interested in measuring such intangible things as customer satisfaction, we can still do this using customer surveys.

Three

Measurements follow a frequency distribution

The range of the data is divided into 'bins' (normally equally sized), and each data point is allocated to the corresponding 'bin'. By plotting the number in each bin against the data range, a frequency histogram will be produced. With a lot of data, the overall envelope shape can be clearly shown as a nice smooth curve.

Four

The most common is the Normal Distribution

This distribution can also be used as a good approximation for many other types of distribution, so you only really need to know about this one (although the others are a lot of fun to study too).

The characteristics of the Normal Distribution are well understood. The centre point is the mean or average (half the measurements are above, and half below). The curve is like a 'bell shape' getting closer and closer to zero but never quite reaching the line.

The 'fatness' (variation) of the curve is measured by the standard deviation, the distance between the mean and the point either side where the curve changes from convex to concave. This distance is also known as the sigma - mathematicians use Greek letters to represent things, and (mu) is used for the mean, and (sigma) is used for the standard deviation.

Five

Most observations fall within three sigma

In fact, if you take all measurements that fall within three sigma of the mean - that is between (mean + 3 sigma) to (mean - 3 sigma), you will have 99.74% of all outcomes.

In practical terms - if you measure the shoe sizes of the entire population, the plotted measurements will look like the Normal Distribution, with a mean (M) and a sigma (S). Almost 100% of all people will have shoe sizes from M-3S to M+3S, so if you make shoes you can satisfy 99.74% of all your customers with just this range of shoe sizes.

Six

Customers have expectations of process performance

Customers of your process will have expectations about the outcome - such as how long it takes, and how well the output suits their needs. Customers of a bank expect to queue to reach the cashier in perhaps 3 minutes or less. Customers in a restaurant expect a certain quantity and quality of food on the plate. Customers purchasing a domestic refrigerator expect it to last, hold temperature, and do what it says in the brochure.

Customer expectation can be determined, and processes can be measured. How well do they match up?

Seven

Three sigma is the current accepted standard

Manufacturers look at what the requirements are, and set the process up so that the outcome has a mean and sigma to fit within these requirements. If the customer has an upper and a lower limit on their requirements or expectations, then the best situation is where the mean is exactly between the customer limits, and the distance between the mean and either limit is three sigma.

When this is working fine the frequency distribution of the measured outcome from the process fits nicely within the customer requirements, and we know that only 0.26% of output will fail to meet those requirements.

Eight

Three sigma is failure 7% of the time

In reality manufacturers set processes up to deliver to customer needs, but there are many customers and they all have different needs. You can't make everyone happy all the time, so what do you do? The accepted practice is to meet the requirements of perhaps just 50-75% of customers - so even if processes are working to +/- three sigma, only half of the customers may like it anyway.

The other problem is that perfection only lasts a short while, and machines often change as parts wear or shift. In services, people change, things become slack, and the variation begins to increase, so less and less of the outcome meets customer requirements.

Today manufacturing and services are becoming more and more complex with hundreds of process steps and thousands of parts. Each bit of the process may deliver at 99% success, but as each part relies on what has gone before the failures soon multiply, and only a very small fraction of the final product gets through without any failure at all.

In reality, three sigma often fails customer requirements 7% of the time. This is not 99.74% as we might think but just 93% customer satisfaction. How often have you had a problem with the car, the washing machine, the utility company, a long queue at the shop? Certainly more often than manufacturers and service providers like to believe or to tell us!

Nine

Six Sigma means failure less than 4 in a million

1. It measures quality in terms of the number of standard deviations (Sigma) between the mean and limits for a process measure. Often this is expressed as 'Defects Per Million Opportunities'. (DPMO / Sigma conversion table)
2. It focuses totally on the customer, and lets the customer decide what matters and lets the customer determine the acceptable limits.
3. It moves the target from three sigma to six sigma. That is a shift from 66,700 to under 4 Defects Per Million Opportunities.

With the limits set by the customer (and not the process owner), and with six standard deviations between mean and limits, failure is experienced by the customer only 3.4 times in every million opportunities, even when process wear and change is accounted for.

Six Sigma quality is about measurable total customer satisfaction.

Ten

Six Sigma is a philosophy, methodology and a quality metric

6s

You now know what Six Sigma is all about. All you need to know is what it means, and how to apply it in practice.

Six Sigma stands for a measure of customer quality - and it stands for a philosophy of giving customers what they want each and every time (zero defects, or as close as you can get). It also stands for a methodology that can be used to change processes and company culture to enable companies to deliver Six Sigma quality.

Six Sigma quality methodology uses the very best from existing Total Quality Management together with Statistical Process Control and Measurement, and strong Customer Focus, and therefore impacts on three key areas: the process, the employee, and the customer. Successful implementation requires Strategy Management and Cultural Change across the entire company. This is not something that you can take lightly or achieve in a day.

Six Sigma is 99.99966% Success for the Customer

• Improvement of existing processes to eliminate the cause of defects
• Design new processes for the perfect successful launch
• Lower costs and higher efficiency lead to more profits

Processes

Employees

• Empowered to change faulty processes and fix problems
• Higher satisfaction and motivation
• Increased efficiency and productivity

Customers

• Engage Total Customer Focus
• Better satisfied customers provide more business and loyalty
• Reduced costs and increased profits