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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.

Imagine a multi-million dollar company that released a product without knowing the probability that it will fail after a certain amount of time. “We offer a 2 year warranty, but we have no idea what percentage of our products fail before 2 years.” Crazy, right? Anybody who wanted to ensure the quality of their product would perform a statistical analysis to look at the reliability and survival of... Continue Reading
To make objective decisions about the processes that are critical to your organization, you often need to examine categorical data. You may know how to use a t-test or ANOVA when you’re comparing measurement data (like weight, length, revenue, and so on), but do you know how to compare attribute or counts data? It easy to do with statistical software like Minitab.  One person may look at this bar... Continue Reading
There's more data available today than ever before, and with statistical software such as Minitab it only takes a couple of seconds to get some significant insights, whether it concerns how to make your business run better or national politics.  For instance, if we look back at the last 9 presidential elections (1980 to 2012), there are some interesting correlations between the percent of state... Continue Reading
When we take pictures with a digital camera or smartphone, what the device really does is capture information in the form of binary code. At the most basic level, our precious photos are really just a bunch of 1s and 0s, but if we were to look at them that way, they'd be pretty unexciting. In its raw state, all that information the camera records is worthless. The 1s and 0s need to be converted... Continue Reading
The difference between defects and defectives lets you answer questions like whether to use a P chart or a U chart in Minitab, so it’s a handy difference to be able to explain. Of course, if you’ve explained it enough times—or if someone’s explained it to you enough times—the whole thing can get a little tired. Fortunately, a new explanation of defects and defectives is one more way we... Continue Reading
When performing a design of experiments (DOE), some factor levels may be very difficult to change—for example, temperature changes for a furnace. Under these circumstances, completely randomizing the order in which tests are run becomes almost impossible.To minimize the number of factor level changes for a Hard-to-Change (HTC) factor, a split-plot design is required. Why Do We Want to Randomize a... Continue Reading
If you want to use data to predict the impact of different variables, whether it's for business or some personal interest, you need to create a model based on the best information you have at your disposal. In this post and subsequent posts throughout the football season, I'm going to share how I've been developing and applying a model for predicting the outcomes of 4th down decisions in Big... Continue Reading
The 1949 film A Connecticut Yankee in King Arthur's Court includes the song “Busy Doing Nothing,” and this could be written about the Null Hypothesis as it is used in statistical analyses.  The words to the song go: We're busy doin' nothin'Workin' the whole day through Tryin' to find lots of things not to do And that summarises the role of the Null Hypothesis perfectly. Let me explain why. What's... Continue Reading
As you may know, we added Bubble Plots to Minitab's menu of meaningful graphs in Release 17. If you are familiar, I think you'll agree that Bubble Plots make a perfect addition to the pantheon of impressive and powerful plots that you can produce in Minitab. They’re great. Of course, they would have been even greater if they used my idea...but that’s spilt milk under the bridge now. If you haven’t... Continue Reading
by Colin Courchesne, guest blogger, representing his Governor's School research team.   High-level research opportunities for high school students are rare; however, that was just what the New Jersey Governor’s School of Engineering and Technology provided.  Bringing together the best and brightest rising seniors from across the state, the Governor’s School, or GSET for short, tasks teams of... Continue Reading
Kappa statistics are commonly used to indicate the degree of agreement of nominal assessments made by multiple appraisers. They are typically used for visual inspection to identify defects. Another example might be inspectors rating defects on TV sets: Do they consistently agree on their classifications of scratches, low picture quality, poor sound?  Another application could be patients examined... Continue Reading
Down 7-0 midway through the 1st quarter of the College Football Playoff National Championship game, Ohio State was facing a 4th and 2 at the Oregon 35 yard line. Buckeye coach Urban Meyer had a decision to make. Attempt a 52 yard field goal, punt and try to pin Oregon deep inside their own territory, or attempt to gain the 2 yards and get a fresh set of downs. Meyer decided to go for it. Ohio... Continue Reading
Statisticians say the darndest things. At least, that's how it can seem if you're not well-versed in statistics.  When I began studying statistics, I approached it as a language. I quickly noticed that compared to other disciplines, statistics has some unique problems with terminology, problems that don't affect most scientific and academic specialties.  For example, dairy science has a highly... Continue Reading
Just 100 years ago, very few statistical tools were available and the field was largely unknown. Since then, there has been an explosion of tools available, as well as ever-increasing awareness and use of statistics.   While most readers of the Minitab Blog are looking to pick up new tools or improve their use of commonly-applied ones, I thought it would be worth stepping back and talking about one... Continue Reading
When you run a regression in Minitab, you receive a huge batch of output, and often it can be hard to know where to start. A lot of times, we get overwhelmed and just go straight to p-values, ignoring a lot of valuable information in the process. This post will give you an introduction to one of the other statistics Minitab displays for you, the VIF, or Variance Inflation Factor.  To start, let's... Continue Reading
If you've read the first two parts of this tale, you know it started when I published a post that involved transforming data for capability analysis. When an astute reader asked why Minitab didn't seem to transform the data outside of the capability analysis, it revealed an oversight that invalidated the original analysis.  I removed the errant post. But to my surprise, the reader who helped me... Continue Reading
Last time, I told you how I had double-checked the analysis in a post that involved running the Johnson transformation on a set of data before doing normal capability analysis on it. A reader asked why the transformation didn't work on the data when you applied it outside of the capability analysis.  I hadn't tried transforming the data that way, but if the transformation worked when performed as... Continue Reading
I don't like the taste of crow. That's a shame, because I'm about to eat a huge helping of it.  I'm going to tell you how I messed up an analysis. But in the process, I learned some new lessons and was reminded of some older ones I should remember to apply more carefully.  This Failure Starts in a Victory My mistake originated in the 2015 Triple Crown victory of American Pharoah. I'm no... Continue Reading
Every now and then I’ll test my Internet speed at home using such sites as http://speedtest.comcast.net  or http://www.att.com/speedtest/.  My need to perform these tests could stem from the cool-looking interfaces they employ on their site, as they display the results using analog speedometers and RPM meters. They could also stem from the validation that I need in "getting what I am paying for,"... Continue Reading
It’s been almost 5 years since I used a quotation from Ghostbusters to introduce one of my early blog posts. But as we’re getting a few bits of entertainment news about the next installment in the Ghostbusters franchise, I thought it might be a good time to talk about busting ghosts in Minitab. In the Minitab sense, ghosts are spaces that are in your data that you can’t see. The busting action is... Continue Reading