dcsimg
 

Statistics

Blog posts and articles about statistical principles in quality improvement methods like Lean and Six Sigma.

Choosing the right type of subgroup in a control chart is crucial. In a rational subgroup, the variability within a subgroup should encompass common causes, random, short-term variability and represent “normal,” “typical,” natural process variations, whereas differences between subgroups are useful to detect drifts in variability over time (due to “special” or “assignable” causes). Variation within... Continue Reading
Everyone loves a Pareto chart. That is, everyone who knows that Pareto charts are a type of bar chart ordered by bar size to help you to determine which bars comprise the vital few that you care about and which are the trivial many that you don't care about. Pareto charts are a great tool for communicating where the largest gains can be made as you focus your improvement efforts. Since I love... Continue Reading
Last time, we went over Bar Charts you could create from Counts of Unique Values. However, sometimes you want to convey more information than just simple counts. For example, you could have a number of parts from different models. The number of occurrences themselves don't offer much value, so you may want a chart displaying the means, sums, or even standard deviations of the different parts.... Continue Reading
A few weeks ago I looked at the number of goals that were being scored in the World Cup. At the time there were 2.9 goals per game, which was the highest since 1970. Unfortunately for spectators who enjoyed the higher scoring goals, this did not last. By the end, the average had fallen to 2.7 goals per game, the same amount scored in the 1998 World Cup. After such a high-scoring start, the goals... Continue Reading
There’s a lot going on in the world, so you might not have noticed that the Organization for Economic Development (OECD) released their new set of health statistics for member nations. On the OECD website, you can now download the free data series for 2014. (Be aware that “for 2014” means that the organization has a pretty good idea about what happened in 2012.) Of course, there’s nothing more fun... Continue Reading
NOTE: This story will reveal how easy it can be to optimize settings using the statistical method called Design of Experiments, but it won't provide easy answers for making your own office coffee any better. After her team’s ultimatum about the wretched office coffee, Jill used the design-of-experiments (DOE) tool in Minitab 17’s Assistant to design and analyze a screening study. Jill now knew... Continue Reading
NOTE: This story reveals how easy it can be to identify important factors using the statistical method called Design of Experiments. It won't provide easy answers for making your own office's coffee any better, but it will show you how you can begin identifying the critical factors that contribute to its quality. At their weekly meeting, her team gave Jill an ultimatum: Make the coffee better. The... Continue Reading
Did you know that this year the American Statistical Association (ASA) is celebrating its 175th anniversary? That’s a pretty significant birthday! On the ASA’s 175thanniversary webpage, they publish blog posts periodically that cover ASA happenings, such as anniversary events and celebrations, as well as interesting tidbits about the organization. Recently, they published a post covering the... Continue Reading
Control charts are some of the most useful tools in statistical science. They track process statistics over time and detect when the mean or standard deviation change from what they have been. The signals that control charts send about special causes can help you zero in on the fastest ways to improve any process, whether you’re making tires, turbines, or trying to improve patient care. I’ve menti... Continue Reading
Via Christi Health, the largest provider of healthcare in Kansas, operates a Center for Clinical Excellence that's made up of a team of quality practitioners, all who have Lean and Six Sigma training. I recently had the opportunity to talk with the team about the types of projects they're working on. I learned not only about the areas of patient care where they are targeting improvements, but about... Continue Reading
After upgrading to the latest and greatest version of our statistical software, Minitab 17, some users have contacted tech support to ask "Wait a minute, where is that Two-Way ANOVA option in Minitab 17?"  The answer is that it’s not there. That’s right! The 2-Way ANOVA option that was available in Minitab 16 and prior versions was removed from Minitab 17.Why would this feature be removed from the... Continue Reading
Previously, I’ve written about when to choose nonlinear regression and how to model curvature with both linear and nonlinear regression. Since then, I’ve received several comments expressing confusion about what differentiates nonlinear equations from linear equations. This confusion is understandable because both types can model curves. So, if it’s not the ability to model a curve, what isthe... Continue Reading
The Minitab Fan section of the Minitab blog is your chance to share with our readers! We always love to hear how you are using Minitab products for quality improvement projects, Lean Six Sigma initiatives, research and data analysis, and more. If our software has helped you, please share your Minitab story, too! Once my Mom was diagnosed with Diabetes Type II, I began to track her blood sugar... Continue Reading
In Part I, Part II, and Part III we shared our experiment, the survey results, and the experimental results. To wrap things up, we're going to see if the survey results tied to the experimental results in any meaningful way... First, we look at whether self-identified knowledge correlated to the total number of correct appraisals: We have no evidence of a relationship (p = 0.795).  So we'll look... Continue Reading
Toolbars are there to make your life easier, but if you don’t take the time to hover over each button and wait for a description, it’s pretty easy to never know that there’s a faster way to do something. The toolbars in Minitab Statistical Software include some pretty nifty shortcuts. Here are my favorite 6: StatGuide As soon as you have results in Minitab, the StatGuide button becomes active on... Continue Reading
In Part I and Part II we learned about the experiment and the survey, respectively. Now we turn our attention to the results... Our first two participants, Danielle and Sheryl, enter the conference room and are given blindfolds as we explain how the experiment will proceed.  As we administer the tasting, the colors of the wine are obvious but we don't know the true types, which have been masked... Continue Reading
Already relaxed on his first day in Napa, Brutus and his wife Suzy decide to visit their favorite winery just before lunch to taste their new Cabernet Sauvignon. The owner recognizes them as they walk in the door and immediately seats them on the patio overlooking the vineyard. Two glasses appear, and as the owner tells them about the new Cabernet, Brutus prepares for an onslaught of blackberry... Continue Reading
A recent study has indicated that female-named hurricanes kill more people than male hurricanes. Of course, the title of that article (and other articles like it) is a bit misleading. The study found a significant interaction between the damage caused by the storm and the perceived masculinity or femininity of the hurricane names. So don’t be confused by stories that suggest all... Continue Reading
You know what really gets on my nerves? A lot of things. That slow, slinky way that cats walk by. Grrrr. The rude, abrupt arrival of delivery persons in their obnoxiously loud trucks. (Why do they always pull up just as I’m settling down for a nap?) Grrrr. Total strangers who reach down and poke me with fat, clumsy fingers that reek of antibacterial soap. Grrrr. And this one always gets my dander up:... Continue Reading
Whether you’re just learning statistics or you're already using data analysis on the job, there are not many tools more straightforward than a bar chart. Bar charts are effective at getting across their message, and are used in a diverse number of fields, from service quality to pharmaceuticals to manufacturing. However, I’ve noticed recently that a lot of customers looking to create a bar chart... Continue Reading