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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.

Last month the ESPN series Outside the Lines reported on major league pitchers suffering serious injuries from being struck in the head by line drives, and efforts MLB is making towards having protective gear developed for pitchers. You can view the report here if you'd like: A couple of things jump out at me from the clip: The overwhelming majority of pitchers are not interested in wearing... Continue Reading
"By publishing the historical data, public dialogue that results from the data release can be more productive because you’ll be able to discuss changes over time." — Denice Ross, 5/17/2015 Last month, President Obama launched the Police Data Initiative. A key goal of the initiative was to make data about police departments more accessible to the public. Twenty-one communities decided to participate... Continue Reading
With their victory in game 6 over the Tampa Bay Lightning, the Chicago Blackhawks won their 3rd Stanley Cup Championship in the last 6 years. This is an incredible feat that no doubt means the Blackhawks have been a very talented hockey team over that stretch. But just like random variation can play a part in quality processes, luck can play a part in sporting outcomes. So how lucky has... Continue Reading
Before I joined Minitab, I worked for many years in Penn State's College of Agricultural Sciences as a writer and editor. I frequently wrote about food science and particularly food safety, as I regularly needed to report on the research being conducted by Penn State's food safety experts, and also edited course materials and bulletins for professionals and consumers about ensuring they had safe... Continue Reading
When data are collected in subgroups, it’s easy to understand how the variation can be calculated within each of the subgroups based the subgroup range or the subgroup standard deviation. When data is not collected in subgroups (so the subgroup size is 1), it may be a little less intuitive to understand how within-subgroup standard deviation is calculated.  How does Minitab Statistical Softwarecalcu... Continue Reading
Previously, I’ve written about how to interpret regression coefficients and their individual P values. I’ve also written about how to interpret R-squared to assess the strength of the relationship between your model and the response variable. Recently I've been asked, how does the F-test of the overall significance and its P value fit in with these other statistics? That’s the topic of this post! In... Continue Reading
When someone gives you data to analyze, you can gauge how your life is going by what you've received. Get a Minitab file, or even comma-separated values, and everything feels fine. Get a PDF file, and you start to think maybe you’re cursed because of your no-good-dirty-rotten-pig-stealing-great-great-grandfather and wish that you were someone else. For those of you who might be in such dire... Continue Reading
I recently fielded an interesting question about the probability and survival plots in Minitab Statistical Software's Reliability/Survival menus: Is there a one-to-one match between the confidence interval points on a probability plot and the confidence interval points on survival plot at a specific percentile? Now, this may seem like an easy question, given that the probabilities on a survival plot... Continue Reading
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
By Matthew Barsalou, guest blogger.   Minitab Statistical Software can assist us in our analysis of data, but we must make judgments when selecting the data for an analysis. A good operational definition can be invaluable for ensuring the data we collect can be effectively analyzed using software. Dr. W. Edwards Deming explains in Out of the Crisis (1989), “An operational definition of safe, round,... Continue Reading
Scientists who use the Hubble Space Telescope to explore the galaxy receive a stream of digitized images in the form binary code. In this state, the information is essentially worthless- these 1s and 0s must first be converted into pictures before the scientists can learn anything from them. The same is true of statistical distributions and parameters that are used to describe sample data. They... Continue Reading
In Minitab Statistical Software, putting a regression line on a scatterplot is as easy as choosing a picture with a regression line on a scatterplot: A neat trick is that you can also add calculated lines onto a scatterplot for comparison or other communication purposes. Here’s a demonstration. United States Sentencing Guidelines The United States Sentencing Guidelines say how people who... Continue Reading
I've never understood the fascination with selfies. Maybe it's because I'm over 50. After surviving the slings and arrows of a half a century on Earth, the minute or two I spend in front of the bathroom mirror each morning is more than enough selfie time for me. Still, when I heard that Microsoft had an online app that estimates the age of any face on a photo, I was intrigued. How would the app... Continue Reading
  The NFL recently announced that after scoring a touchdown, teams will be required to kick the extra point from the 15 yard line as opposed to the 2 yard line. This is a pretty big change. And whether you’re trying to improve the quality of your process, or simply trying to make a sporting event more exciting, it’s always good to know what kind of effects your change will have. So I’m going to use... Continue Reading
In my previous post, I showed you that the coefficients are different when choosing (-1,0,1) vs (1,0) coding schemes for General Linear Model (or Regression).  We used the two different equations to calculate the same fitted values. Here I will focus on showing what the different coefficients represent.  Let's use the data and models from the last blog post: We can display the means for each level... Continue Reading
Since Minitab 17 Statistical Software launched in February 2014, we've gotten great feedback from many people have been using the General Linear Model and Regression tools. But in speaking with people as part of Minitab's Technical Support team, I've found many are noticing that there are two coding schemes available with each. We frequently get calls from people asking how the coding scheme you... Continue Reading
Earlier, I wrote about the different types of data statisticians typically encounter. In this post, we're going to look at why, when given a choice in the matter, we prefer to analyze continuous data rather than categorical/attribute or discrete data.  As a reminder, when we assign something to a group or give it a name, we have created attribute or categorical data.  If we count something, like... Continue Reading
Over the past few years, the average length of an MLB game has been steadily increasing. We can create a quick time series plot in Minitab Statistical Software to display this: As games have been lasting longer, there's been a feeling shared by many that this was a negative. Games seemed to drag on, with a lot of unnecessary stoppages and breaks. To combat this trend, and to try to speed up games to... Continue Reading
In my previous post, I wrote about the hypothesis testing ban in the Journal of Basic and Applied Social Psychology. I showed how P values and confidence intervals provide important information that descriptive statistics alone don’t provide. In this post, I'll cover the editors’ concerns about hypothesis testing and how to avoid the problems they describe. The editors describe hypothesis testing... Continue Reading
If you’ve checked out What’s New in Minitab 17, you’ve had the chance to see that Conditional Formatting leads the list. If you’ve been reading the Minitab blog, you’ve had the chance to see demonstrations with Marvel’s Avengers and the Human Development Index. But you might not have had a chance to see that you can highlight large standardized residuals from a regression model and that the... Continue Reading