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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.

Have you ever wanted to know the odds of something happening, or not happening?  It's the kind of question that students are frequently asked to calculate by hand in introductory statistics classes, and going through that exercise is a good way to become familiar with the mathematical formulas the underlie probability (and hence, all of statistics).  But let's be honest: when class is over, most... Continue Reading
Genichi Taguchi is famous for his pioneering methods of robust quality engineering. One of the major contributions that he made to quality improvement methods is Taguchi designs. Designed experiments were first used by agronomists during the last century. This method seemed highly theoretical at first, and was initially restricted to agronomy. Taguchi made the designed experiment approach more... Continue Reading

7 Deadly Statistical Sins Even the Experts Make

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In its industry guidance to companies that manufacture drugs and biological products for people and animals, the Food and Drug Administration (FDA) recommends three stages for process validation. While my last post covered statistical tools for the Process Design stage, here we will focus on the statistical techniques typically utilized for the second stage, Process Qualification. Stage 2: Process... Continue Reading
Have you ever wished your control charts were better?  More effective and user-friendly?  Easier to understand and act on?  In this post, I'll share some simple ways to make SPC monitoring more effective in Minitab. Common Problems with SPC Control Charts I worked for several years in a large manufacturing plant in which control charts played a very important role. Virtually thousands of SPC... Continue Reading
In the first part of this series, we saw how conflicting opinions about a subjective factor can create business problems. In part 2, we used Minitab's Assistant feature to set up an attribute agreement analysis study that will provide a better understanding of where and when such disagreements occur.  We asked four loan application reviewers to reject or approve 30  selected applications, two... Continue Reading
Did you ever wonder why statistical analyses and concepts often have such weird, cryptic names? One conspiracy theory points to the workings of a secret committee called the ICSSNN. The International Committee for Sadistic Statistical Nomenclature and Numerophobia was formed solely to befuddle and subjugate the masses. Its mission: To select the most awkward, obscure, and confusing name possible... Continue Reading
T'was the season for toys recently, and Christmas day found me playing around with a classic, the Etch-a-Sketch. As I noodled with the knobs, I had a sudden flash of recognition: my drawing reminded me of the Empirical CDF Plot in Minitab Statistical Software. Did you just ask, "What's a CDF plot? And what's so empirical about it?" Both very good questions. Let's start with the first, and we'll... Continue Reading
Previously, I discussed how business problems arise when people have conflicting opinions about a subjective factor, such as whether something is the right color or not, or whether a job applicant is qualified for a position. The key to resolving such honest disagreements and handling future decisions more consistently is a statistical tool called attribute agreement analysis. In this post, we'll... Continue Reading
While there are many graph options available in Minitab’s Graph menu, there is no direct option to generate a waterfall chart. This type of graph helps visualize the cumulative effect of sequentially introducing positive or negative values. In this post, I’ll show you the steps to follow to make Minitab display a waterfall chart even without a "waterfall chart" tool. If you don’t already have... Continue Reading
In my last post on DMAIC tools for the Define phase, we reviewed various graphs and stats typically used to define project goals and customer deliverables. Let’s now move along to the tools you can use in Minitab Statistical Software to conduct the Measure phase. Measure Phase Methodology The goal of this phase is to measure the process to determine its current performance and quantify the problem.... Continue Reading
People frequently have different opinions. Usually that's fine—if everybody thought the same way, life would be pretty boring—but many business decisions are based on opinion. And when different people in an organization reach different conclusions about the same business situation, problems follow.  Inconsistency and poor quality result when people being asked to make yes / no, pass / fail, and... Continue Reading
Process validation is vital to the success of companies that manufacture drugs and biological products for people and animals. According to the FDA guidelines published by the U.S. Department of Health and Human Services: “Process validation is defined as the collection and evaluation of data, from the process design state through commercial production, which establishes scientific evidence that a... Continue Reading
Ahoy, matey! Ye’ve come to the right place to learn about Value Stream Maps (VSM).  Just as a treasure map can lead a band o’ pirates to buried treasures, so too can the VSM lead a process improvement bilge rat to the loot buried deep inside a process! Minitab’s Quality Companion has an easy-to-use VSM tool to guide yer way. Use a value stream map to illustrate the flow of materials... Continue Reading
by Matthew Barsalou, guest blogger The great Dr. Seuss tells of Mr. Plunger, who is the custodian at Diffendoofer School on the corner of Dinkzoober and Dinzott in the town of Dinkerville. The good Mr. Plunger “keeps the whole school clean” using a supper-zooper-flooper-do. Unfortunately, Dr. Seuss fails to tell us where the supper-zooper-flooper-do came from and if the production process was... Continue Reading
When you’re working in Minitab and prepping your data for analysis, it’s common to group data into categories that imply a specific order, such as Low, Medium, High or Beginning, Middle, End. But if the data were to appear in a different order in tables and graphs (for example, Beginning, End, Middle), the result could be confusing, and might distract from your message. Fortunately, with Minitab’s va... Continue Reading
In week 16 of the 2016 NFL season, the Cleveland Browns were able to avoid going into the history books as only the second team to finish the season 0-16. They claimed their first and only win of the season after San Diego missed a last-second field goal. While they came very close to going winless, the statistics paint a very different picture of the odds of that occurrence.  Going 0-16 is hard. Usi... Continue Reading
Did you ever get a pair of jeans or a shirt that you liked, but didn't quite fit you perfectly? That happened to me a few months ago. The jeans looked good, and they were very well made, but it took a while before I was comfortable wearing them. I much prefer it when I can get a pair with a perfect fit, that feel like I was born in them, with no period of "adjustment."  So which pair do you think I... Continue Reading
The language of statistics is a funny thing, but there usually isn't much to laugh at in the consequences that can follow when misunderstandings occur between statisticians and non-statisticians. We see these consequences frequently in the media, when new studies—that usually contradict previous ones—are breathlessly related, as if their findings were incontrovertible facts. Similar, though less... Continue Reading
Want to learn some simple tricks for preparing your graphs for presentation—specifically, how to add footnotes to your graphs, display your graphs in one layout, and add objects (shapes, text, etc.) to make your graphs easier to interpret? Below I’ll share three tips that can help you get your Minitab graphs presentation-ready! 1. Add a footnote to a graph: If you’re looking to add a footnote while... Continue Reading
For all you creative and fun-loving folks out there, in this blog post I'm going to share a puzzle instead of a story or lesson. The holiday season is getting into full swing here in the United States, and that gives us an opportunity to pause and reflect, and even have a little fun while still thinking about how we can improve our processes and products.   Perhaps you're wondering what a puzzle... Continue Reading