Tips and Techniques for Statistics and Quality Improvement

Blog posts and articles about using Minitab software in quality improvement projects, research, and more.

In my previous blog post, I showed how omitting a confounding predictor from a linear regression model obscured the significance of another predictor variable. Confounding variables can be insidious because you don’t always know about them, and you may have to deduce their existence.  In that vein, this post is like a mystery story. I’ll set up the mystery and include the clues. You put on your... Continue Reading
"I could even predict that John Madden will be the next president and make the Turducken our new national bird!" Yes, but what do the data say?  Anybody can predict the future. It’s true. Whether it’s predicting whether a coin will be heads or tails or a quality improvement expert predicting ways to save money, anybody can do it. I could even predict that John Madden will be the next president and... Continue Reading


Smarter Process Improvement

with Companion by Minitab

Have you ever thought that certain Lean Six Sigma practices might be beneficial for your marriage? Although I’m just a newlywed, I’ve had success with these Lean relationship tips in my brief time as a wife.   WIP, JIT, and Poka Yoke’s Take the ‘Honey-Do’ List to a Whole New Level I’ve been told by my husband that long to-do lists stress him out and overwhelm him so much that he loses his focus and... 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
In a previous post, I told you how omitting the subject's weight led to a surprising result in a preliminary regression analysis of the effects of physical activity on bone density. It's a good example of why you need to be very careful about the data you collect: factors you DO NOT include sometimes have a big influence on the ones you DO include! Let's look at how this played out in my... Continue Reading
They were careless people, Tom and Daisy—they smashed up things and creatures and then retreated back into their money or their vast carelessness, or whatever it was that kept them together, and let other people clean up the mess they had made. — F. Scott Fitzgerald As Nick learns in The Great Gatsby, you can't be careless about your friends or you'll create a big mess. You don't want to be riding... Continue Reading
If you’re a quality improvement expert, you already know that statistics can be a powerful tool in your quest to reduce the cost of poor quality and save money. But statistics might be even more powerful than you think—it may actually have helped someone win a lottery jackpot. According to Business Insider, a former mathematics professor with a Ph.D. in statistics has won the Texas lottery... Continue Reading
I’ve been using process analysis to develop a draft strategy for Fantasy Football. I’ve already shown that getting a top running back should be your first priority. But what if the top running backs are gone by the time you get your first pick? When should you switch to other positions? I’ll use Minitab to find out. Analyzing the Data I’ll look at standard deviations, which measure the spread in the... Continue Reading
Control charts are simple but very powerful tools that can help you determine whether a process is in control (meaning it has only random, normal variation) or out of control (meaning it shows unusual variation, probably due to a "special cause"). In an earlier post, I wrote about the common elements that all control charts share: upper and lower control limits, an expected variation region, and... Continue Reading
Riddle: What two tools in Minitab can be used to perform the same analysis on your data? Well, there are probably a few pairs that can be mentioned, but I am going to focus on Discriminant Analysis and Binary Logistic Regression.These tools can be used to predict group membership.  If we look at exh_mvar.mtw, located in Minitab’s sample data folder, we have the perfect data set to use. Here is a... Continue Reading
When we collect data for quality improvement projects, we try to identify and measure all the factors that could influence our outcome.  In scientific research studies, we try to neatly organize, classify, and measure all relevant aspects of the subject matter in order to quantify the relationship between all significant variables.The problem is that reality can be messy and hard to measure,... Continue Reading
I’m relatively new to Lean Six Sigma terminologies and when I first heard someone refer to a “poka yoke,” I thought, “hmm… that must be a new dance move.” I quickly learned that a poka yoke is not a new way to get funky on the dance floor—but rather a term coined by Japanese industrial process engineer Shigeo Shingo to refer to methods that can be used to “mistake-proof” a process.Keeping your... Continue Reading
Most people are familiar with the concept of statistics based on exposure to every-day information, such as people polls, election results, weather or sports stats, commercial product comparisons, etc. Someone collects a set of data, does some number-crunching, and produces for us some interesting statistics. These sorts of sample statistics are called ‘descriptive statistics’. Descriptive... Continue Reading
Now that it looks like we’re going to have an NFL season, it’s time for Minitab to start thinking about Fantasy Football! Many businesses use process analysis to improve performance, so why can’t we do the same thing with the process of selecting a Fantasy Football team? The answer is, we can! I’ll use process analysis to show how you can improve the process of drafting your team. In the Fantasy... Continue Reading
Data analysis is easier when you use Minitab. But before we can practice statistics in Minitab, the data has to be there. So for this post, we’re going to try getting some data into Minitab. Fortunately, data’s all around us and you can choose something that appeals to you.One of my favorite things is literature. I think that one of the great things about Bartleby.com, and other sites that collect... Continue Reading
Lately, I've been thinking a lot about the "perfect" proportion. We’re adding a sunroom to our house and debating the best dimensions for the rectangular addition. Naturally, "the golden ratio" is an enticing option. Also called the Divine Proportion, the golden ratio has gotten a lot of buzz over the centuries. Its basis is simple yet profound. Take a line segment and divide it into two segments... 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
As you probably noticed, the field of statistics is a strange beast. Need more evidence? Linear regression can produce curved lines and nonlinear regression is not named for its curved lines. So, when should you use Nonlinear Regression over one of our linear methods, such as Regression, Best Subsets, or Stepwise Regression? Generally speaking, you should try linear regression first. It’s easier... Continue Reading
Elections are fast approaching, and you might be wondering how reliable can results from exit polls really be? In other words, can you tell with certain confidence which candidate will win prior to the actual election? In particular, consider the state governor elections.Let’s suppose for the sake of simplicity that only two candidates are running – Candidate A and Candidate B.  If we split... Continue Reading
Well, it is quite another superhero movie filled summer for Hollywood. Marvel Comics, owner of popular superheroes such as Spider-Man and Iron Man, is producing movies for each character that will appear in the upcoming 2013 vehicle entitled ‘The Avengers.’ DC Comics, most famous for their characters Batman and Superman, is trying to get more of their relatively unknown characters onto the big... Continue Reading