6 Tools for Applying Six Sigma to the User Experience

Jeff Sauro, PhD

Six Sigma is a methodology for improving the quality of everything from the manufacturing of minute electronic parts to the development of complex software.

At its core, it has a set of tools that helps identify and eliminate defects, waste and undesirable outcomes.

While there are many tools in the six sigma toolbox, here are six that we apply when improving the user experience of websites, software and hardware:

  1. Voice of the Customer: The Voice of the Customer, or VOC, is often a broad term used to mean collecting any data from users or customers. This includes usability tests, interviews and contextual inquiries that all collect data from customers.One of the most potent methods we use is the Top Task survey and analysis. One of the biggest disconnects we see on websites and software is not the color of buttons or the layout of the page, but rather a fundamental disconnect from what users want to do and what designers think users want to do. A simple process of having a representative group of users pick the top five tasks from a comprehensive list helps identify the critical few tasks. You can’t do everything well, but if you get these critical few tasks right, users will notice, return and tell their friends.
  2. Pareto: The Pareto Principal is often called the 80/20 rule and refers to a phenomenon noticed hundreds of years ago with the ownership of land in Italy. Vilfredo Pareto noticed that the majority of land was owed by a minority of people. The process of identifying break points for features, comments, tasks or usability problems can be achieved by using a Pareto analysis. In practice, 20% of customers, comments or problems don’t always account for exactly 80% of the revenue, feedback or usability annoyances. The figures vary but the real benefit is gained by identifying the minority of items that account for the majority of the impact.
  3. Hypothesis Testing: Instead of approaching design decisions with pure instinct and arguments in conference rooms, form a testable statement, invite users, define metrics, collect data and draw a conclusion. Hypothesis testing is the heart of modern statistical thinking and a core part of the Lean methodology. Even before you collect any data, there is an immediate benefit gained from forming hypotheses. It forces you and your team to think through the assumptions in your designs and business decisions.
  4. Quality Function Deployment (QFD) : The QFD provides a structured way to prioritize features, functions or even website content by taking into account both business priorities (the voice of the company) and the customer/user priorities (the voice of the customer). To prioritize, the QFD separates what you do from how you do it. The output is a matrix with features in ranked order of importance.
  5. Cause and Effect Diagram (fishbone): Task failures, errors and long task times are usually the symptoms of multiple underlying problems. These can be problems in the interface or a disconnection with the user’s goals. Through the process of asking “Why?” multiple times and segmenting different causes, you can help identify and address root problems in the user experience. The output of this process is a diagram that looks like a fishbone, hence its alternative moniker.
  6. Failure Modes Effects Analysis (FMEA): Things don’t always go as planned. Errors and failures are inevitable when providing functions for users. However, not all problems are created equal. Some are nuisances while others lead to interface disasters. The FMEA takes into account problem frequency, severity and ability to detect in order to generate a Risk Priority Number (RPN) as a systematic mechanism for focusing on the most critical problems.
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