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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.

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

7 Deadly Statistical Sins Even the Experts Make

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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
July 8th is Math 2.0 Day, a celebration of math intermingling with technology! Have you ever wondered what life was like before we had advanced software to help us perform data analysis? I thought it might be fun to chronicle the evolution of Minitab Statistical Software. Where we’ve come …   In 1972, three Penn State faculty members developed Minitab Statistical Software with the goal 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
We humans do have a tendency to succumb to gold rush fever. And this can happen even in the left-brained, rational field of statistics. After we collect our data, it’s difficult to resist the urge to desperately dash for p-values, as if they were 70% off at Macy’s the day after Thanksgiving.But no matter how well-versed you are in statistics, it’s good practice to get into the habit of intuitively... Continue Reading
In an earlier post, I focused on using Minitab to present the coupon data I collected from my e-mail inbox into a bar chart. The bar chart made it easy for me to visually analyze which days of the week are better or worse for receiving the best coupons from my favorite retailers. As a reminder, here’s how I ranked each coupon’s worthiness: Not worth your timeOffering average savings (A “noteworthy”... Continue Reading
  Time series plots help us see variations over time by displaying observations on the y-axis against equally spaced time intervals on the x-axis. In Lean Six Sigma, they can show you the before-and-after effects of a process change. I recently used a time series plot to see how the price of gold has changed over time. After reaching record highs recently, gold prices have dipped, although some... Continue Reading
It’s summer and maybe you’re traveling to Florida’s coast for a beach vacation (or just wishing you were, like I am)! I got the chance to talk to Dr. Henry Briceño from the Southeast Environmental Research Center (SERC) about how he and his team use statistics to monitor Florida’s water quality. The center’s research projects throughout South Florida have provided a basis for management decisions... Continue Reading
Ever feel frustrated with the flip-floppy results reported in the medical news? Today a cup of coffee will lead you to an early grave. Tomorrow it will ensure that you’ll be dancing a jig on your 99th birthday. Every day, it seems there’s a new study that contradicts a previous finding.   In response, some people throw up their hands in helplessness. Others shrug—then chug another double-shot of... Continue Reading
Statistics can be confusing, especially when you look under the hood at the mathematical engines that underlie it. That's why we use statistical software to do so much of the work for us, and why we use tools like p-values to help us make sense of what our data are saying.The p-value is used in basic statistics, linear models, reliability, multivariate analysis, and many other methods. It's a ... Continue Reading
When you're looking at the results of data analysis, it's always good to keep in mind what different analyses do and don't "prove." This is especially true when you're reading about health-related studies in the popular press.For whatever reason, the media frequently imply that a study has revealed some cause-and-effect relationship, even when the study's authors detail precisely the limitations... Continue Reading