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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.

The NBA playoffs are under way, and all eyes are on LeBron James to see if he can finally bring a championship to Cleveland. But one could argue that there is even a bigger storyline going on: whether Tim Duncan can equal Michael Jordan’s six NBA Championships. Duncan is currently in his 18th season in the NBA, and he is still playing at a very high level. Yet, he’s never in the conversation when... Continue Reading
Generally speaking, I have a problem with authority. I don’t like being told what to do or how to do it. I’m not proud of that. I recall debating with my High School Trigonometry teacher regarding the value of the homework “process.” Specifically, in those situations where the student in question did not require practice to get an A. And, if said student was getting a 98% on the exams, why spend... Continue Reading
Many of the things you need to monitor can be measured in a concrete, objective way, such as an item's weight or length. But, many important characteristics are more subjective, such as the collaborative culture of the workplace, or an individual's political outlook. A survey is an excellent way to measure these kinds of characteristics. To better understand a characteristic, a researcher asks... Continue Reading
A while back, I offered an overview of process capability analysis that emphasized the importance of matching your analysis to the distribution of your data. If you're already familiar with different types of distributions, Minitab makes it easy to identify what type of data you're working with, or to transform your data to approximate the normal distribution. But what if you're not so great with... Continue Reading
The 2016 presidential race is becoming more real. We’ve had several announcements with Ted Cruz, Rand Paul, Hillary Clinton, and Marco Rubio officially entering the race to be President. While the prospective Democratic candidates are down to one, or at most a few, the Republican field is extra-large this election cycle. The first order of business for a GOP candidate is to survive the nomination... Continue Reading
A few times a year, the Bureau of Labor Statistics (BLS) publishes a Spotlight on Statistics Article. The first such article of 2015 recently arrived, providing analysis of trends in long-term unemployment.  Certainly an interesting read on its own, but some of the included data gives us a good opportunity to look at how thought can improve your regression analysis. Fortunately, Minitab Statistical... Continue Reading
In 1898, Russian economist Ladislaus Bortkiewicz published his first statistics book entitled Das Gesetz der keinem Zahlen, in which he included an example that eventually became famous for illustrating the Poisson distribution. Bortkiewicz researched the annual deaths by horse kicks in the Prussian Army from 1875-1984. Data was recorded from 14 different army corps, with one being the Guard... Continue Reading
The Cp and Cpk are well known capability indices commonly used to ensure that a process spread is as small as possible compared to the tolerance interval (Cp), or that it stays well within specifications (Cpk). Yet another type of capability index exists: the Cpm, which is much less known and used less frequently. The main difference between the Cpm and the other capability indices is that the... Continue Reading
The two previous posts in this series focused on manipulating data using Minitab’s calculator and the Data menu. In this third and final post, we continue to explore helpful features for working with text data and will focus on some new features in Minitab 17.2’s Editor menu. Using the Editor Menu  The Editor menu is unique in that the options displayed depend on what is currently active... Continue Reading
My previous post focused on manipulating text data using Minitab’s calculator. In this post we continue to explore some of the useful tools for working with text data, and here we’ll focus on Minitab 17.2’s Data menu. This is the second in a 3-part series, and in the final post we’ll look at the new features in Minitab 17.2’s Editor menu. Using the Data Menu When I think of the Data menu, I think... Continue Reading
With Minitab, it’s easy to create graphs and manage numeric, date/time and text data.  Now Minitab 17.2’s enhanced data manipulation features make it even easier to work with text data. This is the first of three posts in which I'm going to focus on various tools in Minitab that are useful when working with text data, including the Calculator, the Data menu, and the Editor menu. Using the Calculator Y... Continue Reading
As a member of Minitab's Technical Support team, I get the opportunity to work with many people using DOE (Design of Experiments). People often will call after they've already chosen their design, run the experiment, and identified the important factors in their process. But now what? They have to find the best settings, but with several factors and responses, what should they do? "I wish I had a... Continue Reading
In this series of posts, I show how hypothesis tests and confidence intervals work by focusing on concepts and graphs rather than equations and numbers.   Previously, I used graphs to show what statistical significance really means. In this post, I’ll explain both confidence intervals and confidence levels, and how they’re closely related to P values and significance levels. How to Correctly... Continue Reading
Minitab 17.2 is available. You can check out all of the new stuff on the What’s New Page, but I would say that a little demonstration is in order. Here are some new shortcuts that make arranging your data easier in Minitab 17.2. Sorting Let’s suppose that you had copied some Human Development Index data into Minitab and wanted to sort countries in the order of their rank. In the past, you would have... Continue Reading
To choose the right statistical analysis, you need to know the distribution of your data. Suppose you want to assess the capability of your process. If you conduct an analysis that assumes the data follow a normal distribution when, in fact, the data are nonnormal, your results will be inaccurate. To avoid this costly error, you must determine the distribution of your data. So, how do you determine... Continue Reading
Imagine that you are watching a race and that you are located close to the finish line. When the first and fastest runners complete the race, the differences in times between them will probably be quite small. Now wait until the last runners arrive and consider their finishing times. For these slowest runners, the differences in completion times will be extremely large. This is due to the fact that... Continue Reading
by Lion "Ari" Ondiappan Arivazhagan, guest blogger.   Predicting project completion times is one of the major challenges project managers face. Project schedule overruns are quite common due to the high uncertainty in estimating the amount of time activities require, a lack of historical data about project completion, organizational culture, inadequate skills, the complex and elaborative nature of... Continue Reading
This is a companion post for a series of blog posts about understanding hypothesis tests. In this series, I create a graphical equivalent to a 1-sample t-test and confidence interval to help you understand how it works more intuitively. This post focuses entirely on the steps required to create the graphs. It’s a fairly technical and task-oriented post designed for those who need to create the... Continue Reading
I always knew I was different. Even as a kid. “Is that me? Way out there in left field?” I asked the doc. “Yes,” he nodded, as he looked at my chart. “I used brushing to identify you on the graph.” I wasn’t sure I liked getting brushed. It felt like my true identify was being detected and displayed in a window for all to see. The doctor must have sensed my discomfort. “It’s not uncommon—even for those... Continue Reading
Monte Carlo simulation has all kinds of useful manufacturing applications. And - in celebration of Pi Day - I thought it would be apropos to show how you can even use Monte Carlo simulation to estimate pi, which of course is the mathematical constant that represents the ratio of a circle’s circumference to its diameter. For our example, let’s start with a circle of radius 1 inscribed within a... Continue Reading