Charts & Diagrams
A Gantt chart is a commonly used for Six Sigma project management, often created using a program such as Microsoft Project, one of the most popular tools used in project monitoring. A Gantt chart allows a project team to track tasks, resources, deadlines and more. It is used throughout the project from planning through project closure.
Pareto charts are a popular tool for DMAIC projects, used most often during the Measure phase to determine which problems are the most prevalent and whether the Pareto principle applies to any given business operation. Pareto charts show data representing a business problem broken out by category, such as types of technical support calls or reasons for product returns. The categories are shown in decreasing order, and the team aims to find one or two issues it can resolve to take care of the majority of problems. Often another Pareto chart is created in the Improve phase to show the contrast between the before and after states.
Control charts are a hallmark of Six Sigma projects, and are based on statistical process control principles. They show a set of data, usually over time, with statistical control limits drawn in. They are used to distinguish common cause and special cause variation, and to view trends over time. There are quite a few types of control charts, but often Six Sigma teams can rely on the simplest, the individuals chart, for data such as time measures and dollar amounts. They are often created using programs such as Minitab or QI Macros for Excel, and are typically used in the Measure, Improve and Control phases of DMAIC.
Project teams create process maps or process flowcharts during the Measure phase of a DMAIC project to gain clarity about how a process works and where variation and inefficiency occur. A process map visually depicts the steps in a process, and in some cases the group or individual who performs the step, or the movement of documents or materials through the process. Process mapping often includes tracking cycle time so that bottlenecks can be identified and overall cycle time reduced. Process maps include activity flowcharts, opportunity flowcharts, and deployment flowcharts.
Most commonly used during the Analyze phase of a DMAIC project, a fishbone allows project teams to organize potential causes for problems and get at root causes. Also called an Ishikawa diagram or cause-and-effect diagram, it can be created on paper or white board in a brainstorming session or via computer once the information is available. The main bones often show categories of problems, such as technology, process, and training, with smaller bones used to depict potential causes in those categories. Several sample fishbones are shown here, though they often contain much more detail with more levels of bones.
A SIPOC diagram is typically created during the Define stage of a DMAIC project. It illustrates who the suppliers are, what the inputs are, what the high-level process is, what outputs are produced, and who the customers are. It is considered a prerequisite for steps in the Measure phase such as gathering Voice of the Customer (VOC) data and creating a detailed process map.
Process Sigma calculation
During the Measure phase of a DMAIC project, the team uses information about customer requirements and process defects to calculate process sigma. This is a measure of the extent to which process performance meets customer requirements, and is related to the amount of process variation and to the specification limits established by gathering customer feedback. In some cases a preliminary measure is available during the Define phase, but it is refined during Measure once more detailed feedback from customers is obtained and the problem statement is clarified.
Brainstorming is a technique often used in Six Sigma projects. In the Analyze phase of DMAIC it is used to come up with a comprehensive list of potential root causes for the problem that project team aims to solve. In the Improve phase or in a Design For Six Sigma (DFSS or DMADV) project, it is used to come up with a creative and thorough list of possible ways of making an improvement or creating a product or service. The keys to brainstorming is to withhold judgment during the idea generating portion and to ensure that everyone involved gets a chance to contribute ideas. It may be necessary to use a variety of brainstorming techniques to get different types of participants contributing and to bring out innovative ideas.
The Kano model is used as part of establishing customer requirements in DMAIC and DMADV projects. It involves gathering data from customers about a product or service to determine which features must be included for them to be satisfied, which features are not expected but would delight them, and which features will lead to greater satisfaction the more they are fulfilled. For example, anyone buying a television now would likely insist that it have remote control and a clear picture and be cable ready, but would not expect it to have a built-in stereo, built-in picture frames, or a self-cleaning screen. And typically, the larger the screen for the price, the better. Business leaders need to be sure that they meet the “must be” requirements or it doesn’t matter what other features and options are provided.
Statistical data analysis
Often DMAIC projects require the use of advanced statistical techniques such as Analysis of Variance (ANOVA), Chi-square analysis, regression analysis, or other tests. In most cases at least a simple t-test or correlation analysis is necessary. Data analysis typically happens during the Measure phase while analyzing detailed data about the process and problem, occasionally in the Analyze phase while confirming root causes, and again in the Improve phase when making the before-and-after comparison.
Design of Experiments
Design of Experiments (DOE) is a technique used in the Improve phase of DMAIC projects to test different variations of a solution to determine which produces the best or desired result. It requires an understanding of how to properly establish sample sizes and conditions for the trials, and is essentially applying the scientific method to a business process. Software such as Minitab can assist with creating a proper DOE for a Six Sigma project.
House of Quality (Quality Function Deployment)
The House of Quality (HOQ) or Quality Function Deployment (QFD) is a core tool used for a Design For Six Sigma project. Using this method, the project team establishes customer requirements, explores metrics for tracking performance relative to those requirements, and evaluates potential means of implementing the final product or service.
This post is part of the series: Six Sigma 101
Learn the basics of Six Sigma project improvement methodology, from the underlying philosophy to the tools and techniques and the challenges that may arise.