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Tips and Techniques for Statistics and Quality Improvement

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

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

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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
Gantt charts are helpful for quality improvement projects because they establish a graphical time line of various activities and their start and finish dates. They can keep your projects organized and completed on time.They’re especially helpful early on in the planning stages because they force you to identify the major steps of the project and estimate the time you and your team will need to... Continue Reading
The great Homer Simpson once said "People can come up with statistics to prove anything." But an accurate statistical analysis can show significant results. So whether you're making important quality improvement decisions or simply studying a subject that you're interested in, make sure you collect data that that eats the entire doughnut. Erm, I mean, paints the entire picture.   I’ve used ANOVA and... Continue Reading
Statistics can get pretty complicated, which is one reason why so many people are intimidated by the idea of data analysis. But even simple analyses can wind up having a big impact on a company's bottom line.You don't need an elephant gun to take care of a mosquito. Similarly, you don't want to devise a 15-factor, full-factorial designed experiment when a much simpler analysis can take care of the... Continue Reading
There's a scene in the movie Apocalypse Now where Captain Willard (Martin Sheen) is puzzling over what his commanders have asked him to do, and even why they're asking him to do it. As the movie progresses, it becomes clear that his project really hasn't been very well thought out. If the commanders in the film had been Lean Six Sigma Black Belts, I wonder how the narrative would have changed. I... Continue Reading
NASA launched its final space shuttle mission last Friday morning with Atlantis’ last journey to the International Space Station. Do the fiery orange flames lifting the shuttle into the sky remind you of anything on a lean value stream map? I thought they looked strikingly similar to a kaizen burst! So in honor of NASA's last mission, I think the comparison makes for a good opportunity to... Continue Reading
Whether we're talking about process improvement or sports, it's always a good idea to see if data analysis supports the ideas you assume to be true. Sometimes the data confirm what you expected to see. But sometimes the data suggest that the "common wisdom" isn't all that wise after all.For instance, sportscasters talk about “parity” all the time. The NFL is frequently assumed to be the... Continue Reading
Lean Six Sigma manufacturing techniques exist to eliminate waste in a company’s processes. One area of wasteful behavior can occur in the transportation of materials from one process line to another—at any stage in the product’s development. Even the transportation of raw materials to your factory can be made leaner, but most times this element is out of your company’s control. However, you can... Continue Reading
You probably know that grocery stores have all sorts of tactics to keep you in the store longer—from making you walk all the way to the back of the store to grab a gallon of milk, to stimulating your senses by playing feel-good music and leading you through the bakery with the smell of fresh baked bread.The marketing gurus behind grocery stores theorize that the longer you’re in the store, the... Continue Reading
Adhering to the proper assumptions in any statistical analysis is very important. And there seems to be an assumption for everything. For this post, I’d like to clear up some confusion about one particular assumption for assessing normality. A data set is normally distributed when the data itself follows a uni-modal bell-shaped curve that is symmetric about its mean. This graph, created from the... Continue Reading
I recently came across a good post about fishbone diagrams on Christian Paulsen's Lean Leadership blog.  Fishbones (also called cause-and-effect, C&E or Ishikawa diagrams) help you brainstorm potential causes of a problem--and see relationships among potential causes. Brainstorming frequently gets a bad rap.  Some people have had bad experiences with brainstorming sessions that were too loose, and... Continue Reading
A 2 proportion test helps you determine whether two population proportions are significantly different -- such as whether the proportion of men who support a candidate is different from the proportion of women who support the same candidate. It uses the null hypothesis that the difference between two population proportions equals some hypothesized value (H0: p1 - p2 = P0), and tests it against an... Continue Reading
Everyone loves the soft feel of a cotton t-shirt! Unfortunately, the very properties that make cotton fabric so soft also make it prone to wrinkling and tearing. Researchers from the National Textile University in Faisalabad, Pakistan embarked on a study to predict the best fabric properties for strong, crease-free cotton—and they used Minitab to help. Cloth manufacturing plants strive to create a... Continue Reading