Lean Six Sigma and its tools have created an impact in the operations of many companies. Lean and Six Sigma tools can be utilized to promote improvements in quality both as a systematic and strategic manner. Most of the taught Lean Six Sigma tools are quality techniques that are not really new. What can be different is simply the application and integration of the tools.
Lean Six Sigma tools are included in its Define-Measure-Analyze-Improve-Control (DMAIC) improvement project execution roadmap. This roadmap’s execution is to create robust processes that let businesses attain standards that are high and in control.
In Lean Six Sigma, data are subjected to analysis in order to better comprehend problems and identify customer needs. The phases of Lean Six Sigma are to quantify possible defects and its causes, along with the reduction of process waste.
I will now address five of the DMAIC tools used in this process improvement methodology:
The 5 Whys
The 5 Whys tool is employed in order to move past the symptoms toward assimilating the actual cause of a problem. By asking the question "Why" five times, a true cause can often be determined.
A great number of organizations rely on the 5 Whys method for many reasons, including it is simple, easy to accomplish, and does not require statistical analysis. The 5 Whys method is ideal when the problem source is from human interactions and/or other quantifiable factors. To apply this methodology, the following steps can be followed:
• Document and elaborate on the problem.
• Question why the problem occurred and come up with possible answers.
• If answers to this question does not lead to a root cause, ask again ″Why″ and again document responses.
• Repeat the process again and again until the root cause has been determined.
Note, you may ask the question "Why" more or less than five times.
The fishbone diagram is also known as a "cause and effect diagram." A fishbone diagram is a structured tool for brainstorming. This cause-and-effect diagram methodology is crafted to aid organizational teams identify potential causes for a described issue. Some people refer to this tool as Ishikawa diagram, named after its developer. The name fishbone originates from the diagram’s fishbone appearance.
With a fishbone brainstorming approach, the session is conducted around categories of causes such as Methods, People, Machines, Equipment, Materials, Environment and Management. To start the process, the team should state the problem. This statement is then followed by brainstorming for root causes to the issue around the chosen categories.
After the team concurs on the problem statement, the question is placed at the head of the fishbone. The primary bones of the fish are composed of drawn lines connected to the statement of the problem. Each of the main bones in the fish address one of the chosen brainstorming categories. Items from the brainstorming session will be documented as lines connected to these main bones.
The histogram is a data-containing graph which addresses the shape, frequency, dispersion and other factors of a measurement. This tool can deliver a visual representation of data, which can be hard to comprehend in other forms of presentations such as a spreadsheet or tabular format.
The histogram can be used to gain understand as to how a process response relates to customer expectations; e.g., existing specifications or targeted objectives such as on-time delivery. This tool can also help address the question of whether the process in use can actually provide a desirable response so that customer requirements can consistently be met.
One advantage of histogram is that this visual presentation or summary can often be understood even with a glance.
A regression analysis can be useful to determine that a process input has a relationship to the output of a process. This knowledge can help identify an input to the process where control is necessary to achieve a desired process-output response.
Possible issues when using regression analysis include:
• Correlation does not imply causation.
• Multicollinearity can cause havoc in an analysis and jeopardize the validity of its conclusions. Multicollinearity occurs when in a regression model two or more of the predictors are moderately or highly correlated.
• A model might not be accurate because a few extreme data points can provide excess leverage that distorts validity of the model.
The above considerations need to be taken into consideration when using regression analysis.
Run Chart/Time Series
A run chart is basically a graph displaying time series information, where the data are sequenced from first to last. This tool can show trends and shifts. However, care needs to be exercised since sometimes a trend may appear to be occurring but this apparent process shift may simply be the result of common-cause variability; i.e., changes in a response because of not-unusual noise variations from the process.
A 30,000-foot-level chart can often be used in lieu of a run chart to separate common-cause variability from special cause and also make a statement of how the process is performing relative to the needs of customers.
As noted earlier, the above tools are just five of the many tools in the Lean Six Sigma tool kit. These five Lean Six Sigma tools are integrated with other Lean Six Sigma techniques when formulating the DMAIC roadmap. More information about the Lean Six Sigma process improvement methodology and Lean Six Sigma tools integration is described in the article "Lean Six Sigma DMAIC Process Improvement Roadmap."