When we collect data to test a hypothesis, we must manage the tradeoff between the size of the sample we collect, the minimum size of the difference or effect that the test will detect, and the power of the test. Say we want to use a hypothesis test to determine if a process has been […]

# Category Archives: Six Sigma

Our Green Belt course includes an exercise where students create a histogram from a file of 100 data values. Here is the histogram of the data, with a normal probability distribution curve superimposed: Students are not asked to comment on the result, but most are unable to resist doing so. The majority who do comment […]

The PDCA cycle (Plan-Do-Check-Act) is an iterative four-step approach for managing and improving products and business processes. Today we will discuss how the PDCA approach is used by sports teams, with an eye toward how this same thinking can be applied to improving the performance of business processes and products. The Plan Phase begins with […]

In our Black Belt program, we make extensive use of Minitab statistical software. The software performs the actual mathematical calculations, relieving the student of the burden of knowing how to do them using paper and pencil. To use Minitab effectively, students must be able to choose the appropriate test or analysis to perform for a […]

One of my Black Belt students recently submitted an interim project report. The goal of her project is to reduce the time it takes to complete a certain transaction. The project Y metric is success rate, where a success is defined as completing the transaction in 24 hours or less. The goal after improvement is […]

In the Improve phase of a Six Sigma project, we typically need to choose between two or more potential solutions to a problem. There are several tools to help in making this decision, one of which is pairwise ranking. Pairwise ranking is used by individuals or teams to qualitatively prioritize a list of alternatives. There […]

When we work on process improvement, we need to check our results to see if the output of the process was changed for the better. There are two ways to evaluate the results, practical significance and statistical significance. We need to verify that the results are significant in both respects. At the risk of stating […]

Our online Green Belt program includes an assignment where students are introduced to Six Sigma by reading a lecture, reading Chapter One in the text, and viewing several videos. They are then challenged to explain how the readings and videos either reinforced or changed their preconceived notion of what Six Sigma is, based on what […]

Students in our Green Belt course analyze and comment on a case study that deals with products that are returned by customers. They are challenged to discuss what was done well in the case and what could have been done better. The products being returned for credit are data storage systems that are suspected of […]

One of the first tasks our Black Belt students are asked to do when completing a project is collect data over time and create control charts for the primary output metric. The purpose of these control charts is to establish baseline performance, and to determine if the process is stable. One of my students is […]