Quality Improvement

Blog posts and articles about using statistics and data analysis to improve quality through methodologies such as Lean and Six Sigma.

When I get to apply tools like the P’ Chart, I get a thrill. What can I say? I’m a huge fan of Minitab® Statistical Software. I won’t claim to be its biggest fan, but let’s just say I’m definitely up there. Probably in the top 50; definitely the top 100. Admittedly, I’m biased. I have a pretty good gig here. But my history with Minitab started more than a decade before I came to work here. As a... Continue Reading
Now that we’ve explored using gummi bears to do a gage Linearity and Bias Study and a Type I Gage Study, it’s time to use gummi bears to practice the third and final type of measurement systems analysis that I’m planning to demonstrate: the gage R&R study."R&R" stands for Repeatability and Reproducibility, which are the two sources of variation we typically evaluate in a gage R&R study.... Continue Reading

7 Deadly Statistical Sins Even the Experts Make

Do you know how to avoid them?

Get the facts >
You know that song "Once in a Lifetime," by Talking Heads?  The one where David Byrne keeps repeating "Same as it ever was"?   "Same as it never was" is more like it. We confront variation constantly.    Think about it. Did you spend exactly the same amount of time commuting to work today as you did yesterday? No? That's variation.    While these planes look identical, some variation exists. But... Continue Reading
In my post Assessing Variability for Quality Improvement, I showed how measuring variability is as important as measuring the mean for a product or service in a quality improvement initiative. The mean, by itself, often tells an incomplete story. Additionally, quality management veterans know that controlling the variability is often more difficult than controlling the mean. If you want to change... Continue Reading
Last time, we set up a worksheet for doing a Gage Linearity and Bias Study in Minitab Statistical Software. This time, we’ll take a look at my sample data and see what we might learn from a Gage Linearity and Bias Study. Getting comfortable with the variation present in measurement systems will go a long way towards building your confidence with quality statistics. Remember too that the... Continue Reading
It looks like I may have gotten my wish: NBA games should start Christmas day, which will be a huge present to a lot of fans. So while I ponder whether to proceed with a second post about statistics related to the lockout, let's shed some light on a different subject. From time to time, Minitab users will call in needing assistance with control charts.  One common problem people encounter... Continue Reading
Manufacturers need to make items that meet a customer’s standards, or they’ll soon be out of business. That’s why quality engineers devote a good deal of time to making sure that processes are able to meet those standards.  The first step is to make sure your process is stable. After all, you can’t predict the performance of an unstable process. But you can predict and improve on a stable process.  I... Continue Reading
Did you know that November is World Quality Month? The American Society for Quality (ASQ) started the annual event last year to celebrate quality and its impact in the world. Throughout the month of November, ASQ will be showcasing the advancements and valuable quality contributions in businesses, communities, and institutions throughout the world.How are we celebrating at Minitab?-Adding new... Continue Reading
Today, we’re going to get ready to do a Gage Linearity and Bias Study with gummi bears. But to do the linearity and bias study, you first have to talk more about how to collect the data. The Gage Linearity and Bias study has a complication that wasn’t present in the Type 1 Gage Study.The point of the gage linearity and bias study is to assess the bias of a gage across its operating range, not just... Continue Reading
We often see an average (a.k.a. the mean) used to summarize a population or a process. For example, a pizza restaurant might state that their mean delivery time is 20 minutes. Deceptively, this seems like a very intuitive measure.While the mean is important, people often react to the variability even more. Variability is a measure of how spread out the data are from the mean. How many times have... Continue Reading
Multivariate statistics can be used to better understand the structure of large data sets, typically customer-related data. Suppose you have a large amount of data about your customers (preferences, degree of satisfaction, expectations, dislikes etc…), and a large number of variables you need to analyze. Your data might seem somewhat chaotic at first, and you might consider the use of many different... Continue Reading
Gummi bears have more to teach us about measurement systems analysis.Today, we’ll look at doing a Type 1 Gage Study, which compares the measurement variation to the specifications for your process, to judge whether a gage is measuring well enough. The Type 1 Gage Study is a starting point because it evaluates accuracy, precision, and consistency, but only for a single case. Later, we’ll look... Continue Reading
What can gummi bears tell us about measurement system analysis?  We're still practicing statistics with gummi bears, because they don't bounce or slide off of popsicle sticks. In my last post, we looked at some factors that might affect how far a gummi bear flies off of a popsicle stick catapult. Next, what we'd really like to do is to pick some factors to study and do a designed experiment to... Continue Reading
When you're conducting a Capability Analysis, do you know which statistic to look at?  We get a fair number of questions about this, so let's explore the question.  In the graph below, you’ll see that there are two categories for Capability Statistics, Potential and Overall:  The Potential (Within) Capability statistics(Cp, CPL…) are based off of the estimate for within standard deviation. Well,... Continue Reading
So I’m standing at my desk last Tuesday, when my legs suddenly turn to Jell-O. Then I notice the overhead lights gently waving. Soon folks are popping out of their offices with quizzical, sometimes queasy expressions. A few phone calls and Internet searches confirm that we have just experienced a very rare, East Coast earthquake. One centered in Virginia but felt from Georgia to Maine. Wow.We were... Continue Reading
I’ve had the opportunity to talk to several quality improvement professionals from companies across many different industries, and I’ve heard about the common challenges practitioners face when they’re completing quality improvement projects. Here's a brief summary:Where do I start?A challenge faced by quality practitioners, especially newer Green Belts, is the breadth of available quality tools... Continue Reading
Recently I've been thinking about common questions that customers ask when running a Gage R&R analysis in Minitab. For example, when you run a Gage R&R, the last result that shows up in the session window is a value for the ‘Number of Distinct Categories’.  This one metric is something that customers seem to overlook when they call to discuss their Gage studies.          This value represents the... Continue Reading
They say "variety is the spice of life," but when it comes to doing business, variation is not your friend. That's why we have control charts. One of these things is not like the others...is it common cause variation you can accept, or special variation that needs to be addressed? Control charts could tell you. We know that a little bit of variation is inevitable, but we tolerate it within... Continue Reading
I was 'lucky' enough to learn about how Betfair, one of the world's largest online sports betting communities, employs quality improvement in their day-to-day business. Here's a snippet of the case study: Betfair turned to Minitab when a crucial process for helping new customers get started needed improvement. The company invests heavily in different marketing activities, including an outbound... Continue Reading
I was reading an article recently about Jackson Pollock, an abstract artist famous for his “drip paintings,” and I became intrigued when I found out his art falls under the category of “process art.” As I learned more about Pollock and his “process,” I started to think about what he could teach us about process improvement.The process Pollock took to make his artwork was very calculated, hence the... Continue Reading