One of the most confusing issues associated with someone saying "I'm using Six Sigma" has to do with what methodology they are actually using. A majority of the time they are using the DMAIC methodology, because they have existing processes that are wasting resources (hence the big savings you've heard about at GE, Honeywell and others over the past years). The remaining minority of Six Sigma practitioners are using a Design For Six Sigma (DFSS) approach to design a new product for Six Sigma quality.

What Is DMAIC?
When most people refer to Six Sigma, they are in fact referring to the DMAIC methodology. The DMAIC methodology should be used when a product or process is in existence at your company but is not meeting customer specification or is not performing adequately.

The DMAIC methodology is almost universally recognized and defined as comprising of the following five phases: Define, Measure, Analyze, Improve and Control. In some businesses, only four phases (Measure, Analyze, Improve and Control) are used; in this case the Define deliverables are then considered pre-work for the project or are included within the Measure phase. I have even heard of DMAIIC, where the first I stands for Improve and the second I stands for Implement.

The DMAIC methodology breaks down as follows:
Define the project goals and customer (internal and external) requirements.
Measure the process to determine current performance.
Analyze and determine the root cause(s) of the defects.
Improve the process by eliminating defect root causes.
Control future process performance.

What Is DFSS?
DFSS is the acronym for Design For Six Sigma. Unlike the DMAIC methodology, the phases or steps of DFSS are not universally recognized or defined -- almost every company or training organization will define DFSS differently. Many times a company will implement DFSS to suit their business, industry and culture; other times they will implement the version of DFSS used by the consulting company assisting in the deployment. Because of this, DFSS is more of an approach than a defined methodology.

DFSS is used to design or re-design a product or service from the ground up. The expected process Sigma level for a DFSS product or service is at least 4.5 (no more than approximately 1 defect per thousand opportunities), but can be 6 Sigma or higher depending the product. Producing such a low defect level from product or service launch means that customer expectations and needs (CTQs) must be completely understood before a design can be completed and implemented.

One popular Design for Six Sigma methodology is called DMADV and retains the same number of letters, number of phases, and general feel as the DMAIC acronym. It rolls off the tongue (duh-mad-vee) in the same fashion as DMAIC (duh-may-ick). The five phases of DMADV are defined as: Define, Measure, Analyze, Design and Verify.
Define the project goals and customer (internal and external) requirements.
Measure and determine customer needs and specifications; benchmark competitors and industry.
Analyze the process options to meet the customer needs.
Design (detailed) the process to meet the customer needs.
Verify the design performance and ability to meet customer needs.

A slight modification on the DMADV methodology is DMADOV (see Discussion Forum sidebar): Design, Measure, Analyze, Design, Optimize and Verify.

There are a few other "flavors" of DFSS that you might be interested to know about: DCCDI, IDOV and DMEDI.

DCCDI is being popularized by Geoff Tennant and is defined as Define, Customer Concept, Design and Implement. You can see that there are many similarities between these phases and the DMADV phases.
Define the project goals.
Customer analysis is completed.
Concept ideas are developed, reviewed and selected.
Design is performed to meet the customer and business specifications.
Implementation is completed to develop and commercialize the product/service.

IDOV is a well known design methodology, especially in the manufacturing world. The IDOV acronym is defined as Identify, Design, Optimize and Validate.
Identify the customer and specifications (CTQ's).
Design translates the customer CTQs into functional requirements and into solution alternatives. A selection process whittles down the list of solutions to the "best" solution.
Optimize uses advanced statistical tools and modeling to predict and optimize the design and performance.
Validate makes sure that the design you've developed will meet the customer CTQs.

DMEDI is being taught by PricewaterhouseCoopers and stands for Define, Measure, Explore, Develop and Implement. I'm sure you won't have much trouble identifying the main objectives in each of these phases based on the title of each phase.

As you can see, the DFSS approach can utilize any of the many possible methodologies. The fact is that all of these DFSS methodologies use the same advanced design tools (Quality Function Deployment, Failure Modes and Effects Analysis, benchmarking, Design of Experiments, simulation, statistical optimization, error proofing, Robust Design, etc.). Each methodology primarily differs in the name of each phase and the number of phases (and, of course, the acronym).