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Statistics

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

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
As we enter late December, snow is falling here on the East Coast of the United States. The official start to winter is on December 21, 2016, but it’s certainly not uncommon to see snowflakes flying before this date. If you live in the U.S., you know the winter of 2015 was one for the record books. In fact, more than 90 inches of snow fell in Boston in the winter of 2015! Have you ever wondered how... Continue Reading

7 Deadly Statistical Sins Even the Experts Make

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The line plot is an incredibly agile but frequently overlooked tool in the quest to better understand your processes. In any process, whether it's baking a cake or processing loan forms, many factors have the potential to affect the outcome. Changing the source of raw materials could affect the strength of plywood a factory produces. Similarly, one method of gluing this plywood might be better... Continue Reading
If you’re familiar with Lean Six Sigma, then you’re familiar with DMAIC. DMAIC is the acronym for Define, Measure, Analyze, Improve and Control. This proven problem-solving strategy provides a structured 5-phase framework to follow when working on an improvement project. This is the first post in a five-part series that focuses on the tools available in Minitab Statistical Software that are most... Continue Reading
It's that time of year again. The time when eggs get nogged, pudding gets figgy, and it becomes socially acceptable to speak in rhyme. So on that note, and with apologies to Clement Clarke Moore, I bring you this timely and heartfelt PSA. Enjoy. Twas the week before Christmas, and I couldn't be bothered, to make sure that our tree, had quite enough water."A sprinkling of needles on the carpet, I... Continue Reading
A member of Minitab's LinkedIn group asked how to create a chart to monitor change by month, specifically comparing last year's data to this year's data. My last post showed how to do this using an Individuals Chart of the differences between this year's and last year's data.  Here's another approach suggested by a participant in the group.  Applying Statistical Thinking An individuals chart of the... Continue Reading
Reliability analysis is the perfect tool for calculating the proportion of items that you can expect to survive for a specified period of time under identical operating conditions. Light bulbs—or lamps—are a classic example. Want to calculate the number of light bulbs expected to fail within 1000 hours? Reliability analysis can help you answer this type of question. But to conduct the analysis... Continue Reading
In Parts 1 and 2 of this blog series, I wrote about how statistical inference uses data from a sample of individuals to reach conclusions about the whole population. That’s a very powerful tool, but you must check your assumptions when you make statistical inferences. Violating any of these assumptions can result in false positives or false negatives, thus invalidating your results.  The common... Continue Reading
Dear Readers, As 2016 comes to a close, it’s time to reflect on the passage of time and changes. As I’m sure you’ve guessed, I love statistics and analyzing data! I also love talking and writing about it. In fact, I’ve been writing statistical blog posts for over five years, and it’s been an absolute blast. John Tukey, the renowned statistician, once said, “The best thing about being a statistician... Continue Reading
by Matt Barsalou, guest blogger I know that Thanksgiving is always on the last Thursday in November, but somehow I failed to notice it was fast approaching until the Monday before Thanksgiving. This led to frantically sending a last-minute invitation, and a hunt for a turkey. I live in Germany and this greatly complicated the matter. Not only is Thanksgiving not celebrated, but also actual turkeys... Continue Reading
Minitab's LinkedIn group is a good place to ask questions and get input from people with experience analyzing data and doing statistics in a wide array of professions. For example, one member asked this question: I am trying to create a chart that can monitor change by month. I have [last year's] data and want to compare it to [this year's] data...what chart should I use, and can I auto-update it?... Continue Reading
This week we’re celebrating the annual Thanksgiving holiday in the United States, which is not only a good time to reflect on the things we’re grateful for, but it’s also a good time to stuff yourself with turkey, mashed potatoes, green bean casserole, and the usual suspects that find their way to the Thanksgiving table! While I’m of course very thankful for my family, friends, home, etc., I’m also... Continue Reading
The season of change is upon us here at Minitab's World Headquarters. The air is crisp and clear and the landscape is ablaze in vibrant fall colors. As I drove to work one recent morning, I couldn't help but soak in the beauty surrounding me and think, "Too bad everything they taught me as a kid was a lie." You see, as a boy growing up in New Hampshire, I was told that the sublime beauty of autumn... Continue Reading
Pareto charts are a special type of bar chart you can use to prioritize almost anything. This makes them very useful in making sound decisions. For example, if you have several possible quality improvement projects, but not enough time or people to do them all now, you can use a Pareto chart to identify which projects have the most potential for making meaningful improvement. Pareto charts look... Continue Reading
At the inaugural Minitab Insights Conference in September, presenters Benjamin Turcan and Jennifer Berner discussed how to present data effectively. Among the considerations they discussed was choosing the right graph. Different graphs are good for different things. Of course, opinions about which graph is best can, and do, differ. Dotplot devotees might decide that they are demonstrably... Continue Reading
Once again, with the arrival of autumn, it's time for a flu shot. I get a flu shot every year even though I know they’re not perfect. I figure they’re a relatively easy and inexpensive way to reduce the chance of having a miserable week. I’ve heard on various news media that their effectiveness is about 60%. But what does 60% effectiveness mean, exactly? How much does this actually reduce the... Continue Reading
In Part 1 of this blog series, I wrote about how statistical inference uses data from a sample of individuals to reach conclusions about the whole population. That’s a very powerful tool, but you must check your assumptions when you make statistical inferences. Violating any of these assumptions can result in false positives or false negatives, thus invalidating your results.  The common data... Continue Reading
If you’re not a statistician, looking through statistical output can sometimes make you feel a bit like Alice in Wonderland. Suddenly, you step into a fantastical world where strange and mysterious phantasms appear out of nowhere.   For example, consider the T and P in your t-test results. “Curiouser and curiouser!” you might exclaim, like Alice, as you gaze at your output. What are these values,... Continue Reading
If your work involves quality improvement, you've at least heard of Design of Experiments (DOE). You probably know it's the most efficient way to optimize and improve your process. But many of us find DOE intimidating, especially if it's not a tool we use often. How do you select an appropriate design, and ensure you've got the right number of factors and levels? And after you've gathered your... Continue Reading
With another Halloween almost upon us, here's a look back at some of the posts we've written about this holiday specifically, and about various creepy things in general. I hope that you enjoy this roundup of 13 scary statistics posts...and that they won't keep you up at night! 1. How to Make Minitab Wear a Halloween Costume As Halloween nears, you can customize your Minitab interface to match the... Continue Reading