Six Sigma and goal-directed design

If you work for a large company, or have one as a client, you’ve probably heard about Six Sigma. Many companies report great success using Six Sigma initiatives to improve the quality of their products and services, measured by increased customer satisfaction and millions of dollars saved.

At the core, Six Sigma and Goal-Directed design share some of the same values and provide tools to solve some of the same problems. Six Sigma seeks to understand and quantify the functions that matter most to users and provide improvements in those most leveraged areas. Goal-Directed design seeks to delight users and increase loyalty by creating products that are powerful and pleasurable to use. Six Sigma identifies and tracks faults "critical to quality" (CTQs). Goal-Directed design uses personas and goals to define and communicate interaction design decisions.

Rising awareness of personas as a tool for understanding user needs and the formalization of interaction design as a professional discipline has led many companies to seek synergy between Six Sigma and Goal-Directed design. At Cooper, we’re often asked "where does Goal-Directed design fit within the Six Sigma DMAIC process?" and "how can I use Goal-Directed methods as a part of my Design for Six Sigma (DFSS) initiative?" In this article I will briefly review Six Sigma concepts, outline some key differences between Six Sigma and Goal-Directed design and discuss how the two methods can be used together most effectively.

What is Six Sigma?

Six Sigma is both a metric and a process. As a metric, it’s a measure of quality. A six sigma process would have only 3.4 defects per million opportunities. A Six Sigma initiative seeks to identify the causes of defects, quantify the impact, make the necessary improvements to reduce defects and measure the results.

Six Sigma initiatives are led by Black Belts, people trained in the Six Sigma methodology. Project teams consist of people with a number of specialties, depending on the initiative.

Classic Six Sigma follows the DMAIC process:

  • Define project goals and customer requirements
  • Measure the current performance
  • Analyze the defect root cause(s)
  • Improve the process by eliminating the cause(s) of defects
  • Control future process performance

Six Sigma started as a manufacturing process quality improvement initiative at Motorola in the early 80’s and was soon adopted by other major companies including GE and Honeywell. Because Six Sigma’s methods focused on quantifiable improvements, project results could be tied directly to dollars saved. Corporations flocked to the process, initiating company-wide Black Belt programs and launching a new industry of Six Sigma consultants to lead Six Sigma initiatives and train more Black Belts.

In the 90’s, Six Sigma methods were adapted for use in non-manufacturing applications including software development and financial services. Companies asked, "if Six Sigma methods are so successful to improve an existing process, why not use the same methods to design a new product that takes customer CTQ’s into account at the start?" Originally intended for manufacturing processes improvement, Six Sigma concepts have now been adapted to design new products and services.

To support this new product design focus, recent trends in Six Sigma include Design for Six Sigma (DFSS), Voice of the Customer (VoC) and the introduction of new methods to collect customer intelligence including market research, focus groups and ethnographic research.

What is Goal-Directed design?

Goal-Directed design is an interaction design methodology. Every feature in a Goal-Directed design can be tied to user research through personas and scenarios. Goal-Directed designs are documented in a design blueprint that communicates the intent, architecture and behavior of the interface in both static screens and storyboards.

At Cooper, we work in small teams of people with specialized roles, including Interaction Designers, Design Communicators and Visual Designers. The design team is responsible for all aspects of the design process including domain and user research, persona and scenario creation, interaction design and communication of the design solution to stakeholders and implementers.

The practices of Goal-Directed design rely on both systematic and creative thinking. We create data models and workflows to define business processes. We model user archetypes as personas to understand their goals and mental models. To find the right interaction design solution, we cast the personas in scenarios and develop design sketches that follow key pathways through the interface. We apply design principles and patterns to build up a solution. As we grow more confident, we define the behavior of less used functions and draw our solution with increasing levels of fidelity. At every step, we document our evolving design so we can communicate with other members of the team.

Using Six Sigma for new product design

When applied to an existing manufacturing process, Six Sigma has produced significant and measurable results. However, as companies develop a more mature Six Sigma culture, they report a sense of "diminishing returns" after they identify and fix the most obvious and serious faults. In this situation, there’s a natural tendency to look upstream to create new products based on user CTQs so there are fewer faults to begin with. Although Design for Six Sigma (DFSS) introduces new tools to identify customer needs and track them in the final product, it lacks a clearly defined method to translate user requirements into design, or communicate that design so it can be understood and built. There are several challenges to creating a good interaction design using Six Sigma methods alone:

Six Sigma teams may lack interaction design skills

Black Belts are trained in the Six Sigma process, project management and statistical analysis. They pull together and manage a team of people for their initiative. Interaction design activities such as planning and conducting user research, creating personas and scenarios and creating a design blueprint are activities that require specialized skills which may not exist within the Black Belt’s team.

The things that are easiest to measure may not be the most important

Problems that are easy to measure aren’t usually the problems you need to fix. For example, it’s easy to measure how long it takes someone to fill out a form and measure how much faster they can fill it out after your project. Interaction design methods, however, can help you reconsider if the form is even necessary at all, and come up with a better solution altogether. User satisfaction is more complex than a lack of defects.

There’s also the issue that according to Six Sigma process, every Black Belt needs to be trained with one or more projects. Since measureable results are critical to the process, it can be tempting to choose a project that’s easy to measure over one that might have more value but is harder to measure.

Voice of the Customer (VoC) does not result in user models

During the VoC stage of DFSS, Six Sigma teams determine and execute a research plan to collect user CTQs. DFSS does not specify what kind of research you need to do and it does not provide methods to translate these findings into user models. Goal-directed design provides a rich set of tools for modeling user needs through personas and scenarios.

To build an accurate model of user needs, you have to talk to the right people and ask the right questions. Lacking time, budget and expertise, Six Sigma teams use focus groups, market research and second-hand information from sales reps or helpdesk staff who talk with customers or users. While these activities will certainly increase the team’s understanding of their users, it will not result in actionable tools that will guide your design decision-making process.

No defined path to turn requirements into design

DFSS does not define how CTQs manifest in the product. A list of requirements is not an actionable blueprint. Users are good at telling you what’s wrong, but they aren’t good at telling you how it should be. Engineers require assistance to prioritize features and understand how they will best be understood by users. Every feature in a Goal-Directed design can be traced back to user research through the persona and scenario.

Associating Six Sigma CTQs with user goals would enable this traceability from research to design, and would also support Six Sigma’s requirement to track requirements into the final product.

There is no design blueprint

Six Sigma doesn’t require that the interaction design be documented, or specify that the design be illustrated with screen sketches or storyboards. Rather, project teams determine the nature and level of communication appropriate for the project.

Clearly communicating design throughout the process is a vital ingredient to creating a coherent design and enabling a feedback process throughout the project. Without clear documentation, there’s no way for stakeholders and implementers to share understanding about what they are going to build and how it will look.

Using Goal-Directed design with Six Sigma

Goal-Directed design techniques can be an excellent compliment to your Six Sigma initiative. A well-designed research plan can help you talk to the right people and ask the right questions. A complete set of personas, based on good ethnographic research can help you understand and communicate the needs of your users to your organization. Six Sigma CTQs can be tied to user goals. Personas and scenarios can inform the development of use cases, test plans and usability trials.

Just as Six Sigma requires training in certain skills before being promoted to a Black Belt, interaction design requires trained, skilled designers for best results. An interaction design team can provide:

Ownership of the interaction design process from user research through development and communication of the design solution.

A design blueprint that will help you communicate the design solution to everyone in the process who needs to participate in product construction and ensure the product is built as it’s envisioned.

For more information about Six Sigma, please see the following resources:

Lane Halley

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