This is the first of a four-part blog on gage R&R. It answers this basic question:

What is a Gage R&R study?

If you google this question, you will get several answers including this one from the www.isixsigma.com dictionary:

“Gage R&R, which stands for gage repeatability and reproducibility, is a statistical tool that measures the amount of variation in the measurement system arising from the measurement device and the people taking the measurement.”

This statement is...

This is the third in a four-part series introducing control charts. The first blog addressed the question of what a control chart is. The second blog explored the relationship between variation and control charts . This blog begins to answer the following question:

What is the purpose of a control chart?

We will continue with the driving to work example shown in the last two blogs to explore three different purposes for a control chart....

This is the start of a four-part blog on control charts. The blogs will answer the following questions:

• What is a control chart?
• What is variation and how does it relate to a control chart?
• What is a control chart used for?
• Where is a control chart used?

Control charts are at the heart of statistical process control (SPC). So maybe we should start with answering what a process is. A process is simply what we do. It can be filling out an expense report, checking a person into a hospital, driving to work, filling a prescription, etc...

Our first two blogs in this process capability series answered two questions: What is process capability? – and - What is Cpk? This blog answers the next question: What is Ppk?

The answer is quite simple. Just to refresh your memory, Cpk is expressed as the following:

Cpk = Minimum (Cpu, Cpl)

Cpu=(USL- X )/3σ

Cpl=( X -LSL)/3σ

where Cpu is the capability based on the upper specification limit (USL), Cpl is the capability based on the lower specification limit (LSL), X...