Statistics Posts for Improvement Insights

Improvement Insights Blog

Latest "Statistics" Posts

Deming’s Insights on Control Charts for Workers

I was rereading Deming’s book “Out of the Crisis,” and discovered a way to use control charts that is new. Deming uses control charts to compare individual worker performance. Deming often asked leaders to drive out fear, but comparing individuals seems like a way to create fear unless you use the results to help train individuals to higher standards of performance. Here’s how:



“Hi, I’m Jay Arthur, author of “Lean Six Sigma Demystified” and QI Macros [software].

“I don’t know about you, but every once in a while I go back and re-read books about Quality. I’ve been getting back into Deming.

Posted by Jay Arthur in Improvement Insights, Jay Arthur Blog, Statistics.

Why Are We Still Talking about Cp/Cpk and Pp/Ppk Formulas?

I found a discussion on MyASQ’s Website about Cpk formulas. Why is anyone talking about how to calculate formulas by hand? It’s a waste of time. Here’s why:



“Hi, I’m Jay Arthur, author of “Lean Six Sigma Demystified” and QI Macros [software].

“This morning I was out on the myASQ website, and there was a question about Cp and Cpk and Ppk formulas and stuff like that. And there was, you know, “Well, standard deviation” and “Why do we have to do R Bar over D2?” or whatever it was, you know. The answers were like, “Well, you know, standard deviation is pretty close to whatever…”

“I was [thinking], “What is the question here?

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

Be A Process Doctor

Medical doctors (M.D.) help people heal. In Lean Six Sigma, we help companies heal. Be a Process Doctor(P.D.).



“Medical doctors diagnose and then treat patients. I think of myself as a Process Doctor: a P.D.; not an M.D., a P.D. I work with companies and I try and figure out why their systems are not working the way they ought to and remove blockages to speed things up. You know, get the electrical systems working better. It’s the same idea. So I think you and I are all Process Doctors.

“Now, I think the metaphor about this is great because we’re in the helping profession and we help things get better and stay better; stay healthy, just like a medical doctor.

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

Is Lean Six Sigma Mired in Old Think?

Is Lean Six Sigma stuck in last century thinking? Maybe we just can’t see it. Here’s what I discovered recently.



“I’m Jay Arthur, author of “Lean Six Sigma Demystified” and QI Macros [software].

“Recently, I discovered something and it got me thinking. Now, if you know anything about calculating formulas for an XbarR chart, you know that what you do is if you have some numbers like a subgroup, maybe they got 3.3 and 3.4 or something like that, what you do is calculate for this subgroup what’s the average of the X’s. Well, in this case it’d be 3.3.

Posted by Jay Arthur in Improvement Insights, Lean, Six Sigma, Statistics.

How Many SPC Books and Formulas Do You Need?

Most people are terrified of statistical formulas. How many do you need to know? I think my answer will surprise you.



“I’m Jay Arthur, author of “Lean Six Sigma Demystified” and QI Macros [software].

“Next to my desk at the office I have dozens of books about Statistical Process Control and Quality Improvement and all the other stuff. How many of those formulas do I think you all need to know?

“My answer is zero. The software will do all of that for you. You do not need to know a single formula. I go to these conferences and I talk to people and I talk about control charts and people all start to get anxious about, “Oh my god, do I have to learn any formulas?”

Posted by Jay Arthur in Improvement Insights, QI Macros, Statistics.

Use Numbers Not Percentages

Ever noticed that when you describe something as a percentage people seem to draw a blank? They may nod, but not understand. Here’s why:



“I’m Jay Arthur, author of “Lean Six Sigma Demystified” and QI Macros [software].

“I want to alert you to something that I discovered when I saw my friend, Dr. Jack ReVelle, speak. Now, if you know anything about control charts, you know that if you have an upper and lower control limit, well, 99.7% of all points should fit between those two things. And I saw Jack talk about this and I realized that nobody can make a picture of a percentage.

Posted by Jay Arthur in Improvement Insights, Statistics.

Think SPC is Too Complex?

Most people are terrified of “statistical” anything. Do you think SPC is too complex? You may not like the alternative.



“Whenever I talk to people about Statistical Process Control, first the word “statistical” scares the living crap out of them. But they say, “Well, you know, uh… I’m not that good with math and formulas,” and I say, “Well, you don’t have to know math and formulas. We’ve got software that’ll do all that for you. What you have to do is know what the chart tells you about what you should do about your process. They’re all a little surprised.

Posted by Jay Arthur in Improvement Insights, Lean, Six Sigma, Statistics.

An Easy Way to Tell if Data is Variable or Attribute

Six Sigma students are often confused by terminology. Variable and attribute data are often confusing. Calling it measured or counted doesn’t help that much. Here’s a way to explain it that almost everyone can understand quickly.



“Early on when I was teaching Quality Improvement, people kind of struggled with the whole idea of variable and attribute data, and telling them that it was measured and counted didn’t seem to help a lot.

“As a programmer, the way I think about it is: If it has a decimal point, it has to be measured, right? If it’s an integer, it’s most likely counted, right?

Posted by Jay Arthur in Improvement Insights, QI Macros, Statistics.

Start Using XmR Charts for All of Your KPIs

Do you spend too much time chasing why one number is too high or another is too low? Are these kinds of wild goose chases wasting time while the real problems go wanting? The XmR chart is the answer to your dreams.



“Dr. Donald Wheeler calls the XmR chart (or Individuals and Moving Range chart) “the Swiss Army knife of control charts.” You can use it for all kinds of things.

“I believe if every company in America started using XmR charts to track all of their key process indicators, I don’t care if it’s financial results or defects or patient length of stay or I don’t care what it is.

Posted by Jay Arthur in Improvement Insights, QI Macros, Statistics.

Arthur’s 4-50 Rule – The Secret to Breakthrough Improvement

We’re all familiar with Pareto’s rule: 20% of causes produce 80% of the results. But are you familiar with Arthur’s 4-50 rule? Typically, 4% of any process – one step out of 35 – is the cause of more than 50% of waste, rework and lost profit.



“Hi, I’m Jay Arthur, author of “Lean Six Sigma for Hospitals” and QI Macros [software].

“Now I’ve probably talked to you about this before, but we’re all familiar with Pareto’s rule that 20% of what you do produces 80% of the mistakes, errors, waste, rework, lost profit. 20% of your customers produce 80% of your revenue.

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