Latest Posts

Use XmR Charts instead of c, np, p and u Charts

I have found that an XmR chart is the easiest way to display attribute data. Simply convert the numerator/denominator into a ratio and plot the ratio. defects per day could be a c chart, but an XmR chart works just as well defects/samplesize could be np, p or u chart, but XmR chart works just as […]

Posted by Jay Arthur in QI Macros, Six Sigma, Statistics.

What USL/LSL Do I Need for Cp>1?

Customer asked me what seemed like a strange question: What specification limits do I need to get a Cp greater than one? Usually her customer should set specification limits, but her boss wanted to know what they could deliver. Hmmmm! Then I realized that since QI Macros templates (e.g., XmR chart) calculate the average and […]

Posted by Jay Arthur in QI Macros, Six Sigma, Statistics.

Cpk and Hard vs Specification Limits

A customer called upset about Cpk. He had a runout of 0.010, but was getting a very low Cpk. Turns out he’d made the classic mistake of confusing a hard limit (e.g., zero) with a specification limit. I had him use QI Macros with an Upper Specification limit (USL) and no Lower Specification Limit (LSL). […]

Posted by Jay Arthur in QI Macros, Six Sigma.

Lean Insights from “The Founder” Movie

Early in the movie, the McDonald’s brothers describe how they came up with the concept for speedy service. It’s Lean. They had too many menu items, so they decide to simplify down to burgers, fries and soft drinks. (Think Lean inventory.) They go to a tennis court and use chalk to lay out a possible […]

Posted by Jay Arthur in healthcare, Lean, Manufacturing, Service.

Mistake-proofing Bathroom Design

My friend, Mary LoVerde’s ezine shows a hotel bathroom she recently experienced. How would you mistake-proof this design? What are the possible failure modes and effects (FMEA)?

Posted by Jay Arthur in QI Macros, Six Sigma.

Is Fear of Math Holding You Back?

Many people avoid Six Sigma because they think it involves a lot of math and statistics. You know, formulas. I don’t think you need any formulas. You don’t need to be a statistician. You just need software that went to college and knows the formulas. In The Math Gene, Author Keith Devlin explores “why so […]

Posted by Jay Arthur in QI Macros, Six Sigma.

New Year’s Resolution – Go On a Raw Data Diet

Most data is preprocessed or overprocessed. All the nutrients that you need to solve problems are gone. Solution: Go on a Raw Data Diet

Posted by Jay Arthur in Data Mining.

Lean Water Work?

Denver Water sent us a letter back in October about upcoming road closures, then delayed it a month. They moved in a bunch of equipment one week. Then over a week later they jumped into action to install part of a new pipeline  just before a big snow storm. Then it was cold for a week. […]

Posted by Jay Arthur in Lean, Service.

Quality Tool Usage at IHI 2016 Poster Presentations

I’ve been monitoring the use of quality tools at the Institute for Healthcare Improvement conference for over a decade. This year there was a slight uptick in the use of control charts, but still far below my expectations. How can healthcare hope to achieve and sustain improvements without control charts? There were over 500 posters, […]

Posted by Jay Arthur in healthcare, QI Macros, Six Sigma.

Statistical Bullies

At IHI, I spoke with one Quality Improvement Adviser who was getting blow back from certain statisticians in her organization. They were challenging her methods and tools and analysis. As I have written before, I call these folks “Stat Bastards” because they belittle others rather than help them. As a member of the American Statistical […]

Posted by Jay Arthur in Six Sigma, Statistics.