In our Green Belt program we have an exercise where students create a histogram from a set of data. Most students use Excel to create their histogram, and here is the resulting graph: When submitting their work, students quite often include a statement to the effect that the data is “normally distributed” because it appears […]

# Author Archives: developers

One of the dilemmas that students face when choosing Six Sigma certification training is whether to attend a live, instructor led course in a traditional classroom setting or an online course. Both types of delivery have pluses and minuses. In the classroom, you will have the benefit of interaction with your instructor and the other […]

I have observed a number of problems and issues with the way that Six Sigma students gather data for, create and interpret control charts. The purpose of this article is to help you avoid these common problems and issues, and to help you understand how to use control charts as part of a Six Sigma […]

The Six Sigma methodology relies on decisions that are made based on facts and data. One of the challenges in the Analyze phase of Six Sigma is being able to identify what is really going on in a process based on the facts and data that were collected in the Measure phase. Another challenge is […]

I am often asked to provide recommendations on how to develop and/or select Six Sigma training programs. An interesting and very useful theory of how people develop and learn is the theory of Multiple Intelligences, developed by Howard Gardner, PhD, Professor of Education at Harvard University. This theory explains that each of us has a […]

One of my Master Black Belt students sent me an inquiry about a manufacturing process that was producing a very small percentage of scrap. He was having trouble understanding the control charts that he had created from his data and was convinced that he needed to perform a transformation on the underlying data. I started […]

One of my Black Belt students recently submitted his final project report. He used the two proportions test in Minitab to compare the proportion of on time performance for completion of employee appraisals, before and after improvement. I sent him the following feedback regarding this test. “Hi. Your null and alternate hypotheses are correctly stated. […]

Although the central limit theorem can seem abstract and devoid of any practical application, this theorem is actually quite important to the practice of statistics. As we will see, this theorem allows us to make some assumptions about a population. In order to understand the basis for the Central Limit Theorem, consider a population of […]

We should constantly strive to provide exactly what the customer wants when working on process improvement. One way to do so is to identify activities that are wasteful and then work to reduce or eliminate those activities. Waste is defined as an activity that consumes resources but does not add any value for the customer. […]

In an earlier article in this series, I introduced some basic issues in measurement systems analysis such as granularity, accuracy, reproducibility, repeatability, stability and linearity. In this article we will explore in more detail how to evaluate the performance of a measurement system with respect to bias and linearity. Gage bias examines the difference between […]