Using Probability Plots to Understand Laser Games Scores

There is more than just the p value in a probability plot—the overall graphical pattern also provides a great deal of useful information. Probability plots are a powerful tool to better understand your data.

In this post, I intend to present the main principles of probability plots and focus on their visual interpretation using some real data.

In probability plots, the data density distribution is transformed into a linear plot. To do this, the cumulative density function (the so-called CDF, cumulating all probabilities below a given threshold) is used (see the graph below). For a normal...

Common Statistical Mistakes You Should Avoid

It's all too easy to make mistakes involving statistics. Powerful statistical software can remove a lot of the difficulty surrounding statistical calculation, reducing the risk of mathematical errors—but  correctly interpreting the results of an analysis can be even more challenging. 

No one knows that better than Minitab's technical trainers. All of our trainers are seasoned statisticians with years of quality improvement experience. They spend most of the year traveling around the country (and around the world) to help people learn to make the best use of Minitab software for analyzing data...

Gage This or Gage That? How the Number of Distinct Categories Relates to the %Study Variation

We cannot improve what we cannot measure. Therefore, it is critical that we conduct a measurement systems analysis (MSA) before we start analyzing our data to make any kind of decisions.

When conducting an MSA for continuous measurements, we typically using a Gage R&R Study. And in these Gage R&R Studies, we look at output such as the percentage study variation (%Study Var, or %SV) and the Number of Distinct Categories (ndc) to assess whether our measurement system is adequate.

Looking at these 2 values to assess a measurement system often leads to questions like "Should I look at both values? ...

A Little Trash Talk: Improving Recycling Processes at Rose-Hulman

The Six Sigma students at Rose-Hulman Institute of Technology are at it again! A few months back, we blogged about the Six Sigma project they did to reduce food waste at the on-campus dining center.

This time, the students—lead by Dr. Diane Evans, Six Sigma black belt and associate professor of mathematics at Rose-Hulman—are performing a Lean Six Sigma project to reduce the amount of recycling thrown in the normal trash cans in all of the institution's academic buildings, including the library. Unfortunately, the recycling bins Rose-Hulman has placed all over its campus are underused, and it’s...

Applying Six Sigma to a Small Operation

Using data analysis and statistics to improve business quality has a long history. But it often seems like most of that history involves huge operations. After all, Six Sigma originated with Motorola, and became adopted by thousands of other businesses after it was adopted by a little-known outfit called General Electric.

There are many case studies and examples of how big companies used Six Sigma methods to save millions of dollars, slash expenses, and improve quality...but when they read about the big dogs getting those kind of results, a lot of folks hear a little voice in their heads...

Use the Minitab Assistant to Choose a Graph

Everyone loves Minitab’s Assistant. My favorite bit, as I’ve shown with the Gage R&R Study, is the way that the Assistant puts all the results you need into reports that are easy to understand and present. But it’s also pretty neat that before you ever choose what to do in Minitab, the Assistant is ready to help you. Let’s take a closer look at the Assistant's Graphical Analysis tools.

Help Me Choose

Choose Assistant > Graphical Analysis and the most prominent thing you’ll see is a question:

But you’re not left with just the three objectives. Select "graph variables over time," and before you...

Is There a World Cup "Group of Death"?

Much is made following the World Cup draw every four years over which group is the “group of death.”  This is generally considered to be a really difficult group that is tough to advance from, although there is no true definition (more on that below).

First, for readers not familiar with World Cup groups, a brief explanation of how teams are “grouped” in the World Cup is in order.  Thirty-two teams qualify to compete, and they are placed into eight different groups labeled A-H, with each having a predetermined “top” team.  In the group stage of the World Cup, each team plays the other three...

Applied Regression Analysis: How to Present and Use the Results to Avoid Costly Mistakes, part 2

Applied regression analysis can be a great decision-making tool because you can predict the average outcome given input values. However, predictions are not as simple as plugging numbers into an equation. In my previous post I showed how a majority of experts vastly underestimated the variability around the predicted outcome in a manner that can lead to costly mistakes.

We also saw how graphing the data is a simple way to avoid these mistakes because it highlights the uncertainty. In this post, I'll explore other techniques that you can use in Minitab statistical software to facilitate good...

Making a Difference in How People Use Data

A colleague of mine at Minitab, Cheryl Pammer, was recently featured in "A Statistician's Journey," a monthly feature that appears in the print and online versions of the American Statistical Association's AMSTAT News magazine.  

Each month, the magazine asks ASA members to talk about the paths they took to get to where they are today. Cheryl is a "user experience designer" at Minitab. In other words, she's one of the people who help determine how our statistical softwaredoes what it does, and tries to make it as helpful, useful, and beneficial as possible. Cheryl is always looking for ways to...

Itchy, Sneezy, Stuffy: Delivering Relief with Nasal Spray and DOE

Recently, a customer called our Technical Support team about a Design of Experiment he was performing in Minitab Statistical Software. After they helped to answer his question, the researcher pointed our team to an interesting DOE he and his colleagues conducted that involved using nasal casts to predict the drug delivery of nasal spray.

The study has already been published, and you can read more about it here, but I wanted to highlight this use of the DOE tools in Minitab in this blog post.

Using Nasal Casts to Predict Nasal Spray Drug Delivery

The nose is a convenient route of administration...

Avoiding a Lean Six Sigma Project Failure, part 3

In previous posts, I’ve outlined some reasons why a Lean Six Sigma project might have been deemed a failure. We’ve gathered many of these reasons from surveying and talking with our customers.

I’d like to present a few more reasons why projects might fail, and then share some “words of wisdom” from Minitab trainers on how you can avoid these project failures.

Forcing Projects into DMAIC

Certain quality improvement projects were never meant to be Six Sigma projects that fit neatly into the DMAIC (Define – Measure – Analyze – Improve – Control) methodology. Examples include:

1. Selecting a vendor...

Using Hypothesis Tests to Bust Myths about the Battle of the Sexes

In my home, we’re huge fans of Mythbusters, the show on Discovery Channel. This fun show mixes science and experiments to prove or disprove various myths, urban legends, and popular beliefs. It’s a great show because it brings the scientific method to life. I’ve written about Mythbusters before to show how, without proper statistical analysis, it’s difficult to know when a result is statistically significant. How much data do you need to collect and how large does the difference need to be?

For this blog, let's look at a more recent Mythbusters episode, “Battle of the Sexes – Round Two.” I...

How Many Licks to the Tootsie Roll Center of a Tootsie Pop? Part 2

by Cory Heid, guest blogger

A few months ago I posted a blog about Tootsie Pops and how many licks it takes to get to the Tootsie Roll center. If you haven’t read the post, here's a quick summary.

Recap of Initial Study

I broke down my experiment into four parts where I would test:

  • the force of a lick
  • temperature of a person's mouth
  • pH level of a person's saliva
  • the solubility of a person's saliva

After some tests and analysis of the data I collected, I was able to conclude that none of the factors I tested were statistically different or important enough to affect the number of licks required to...

Doing Gage R&R at the Microscopic Level

by Dan Wolfe, guest blogger

How would you measure a hole that was allowed to vary one tenth the size of a human hair? What if the warmth from holding the part in your hand could take the measurement from good to bad? These are the types of problems that must be dealt with when measuring at the micron level.

As a Six Sigma professional, that was the challenge I was given when Tenneco entered into high-precision manufacturing. In Six Sigma projects “gage studies” and “Measurement System Analysis (MSA)” are used to make sure measurements are reliable and repeatable. It’s tough to imagine doing that...

Quartile Analysis for Process Improvement

The value of analyzing data is well established in industries like manufacturing and mining, but data-driven process and quality improvement is increasingly being adopted in service industries like retail sales and healthcare, too. In this blog post, I'll discuss how a simple data analysis may be used to improve processes in the service sector.

Suppose we want to improve the way incoming calls are processed in a call center run by a large insurance company. We are interested in analyzing duration metrics, which are very useful in assessing both the experience of customers—who always...

Spicy Statistics and Attribute Agreement Analysis

My husband, Sean, and I were recently at my parent’s house for a picnic dinner. As a lover of hot sauce (I’m talking extremely hot, hot, hot, HOT sauce!), my stepdad always has a plethora of bottles around to try. While I do enjoy spicy foods from time to time, I’ve learned not to touch his hot sauce selections. His favorites are much too spicy for my taste!

Unfortunately, Sean learned the hard way. He used Habanero hot sauce on his hot sausage sandwich – talk about double the heat! I saw him sinking in his seat, eyes watering … a few hoarse coughs …

Yikes!  Anyway, Sean is alive and well after...

Minitab's LinkedIn Group: A Great Place to Talk Stats

If you've got questions about quality improvement and statistics, I've got a resource for you: the Minitab Network on LinkedIn. I'm privileged to serve as the moderator of this group, which lets people who use Minitab products communicate and network with like-minded people from around the world.

LinkedIn is the leading social networking site for professionals, and the Minitab Network on LinkedIn has become an excellent way for Minitab users to share ideas and learn from each other. Since we launched the group in August 2008, it's become a very active community of people who share an interest...

Lean Six Sigma in the Classroom: Preparing Students for Careers in Quality Improvement

I recently had the opportunity to talk with Ken Jones, professor of operations and supply chain management at Indiana State University, about a business process improvement course he teaches at the university. The course covers a variety of Lean Six Sigma tools and techniques and gives students the opportunity to team with local businesses to complete real quality improvement projects. Upon successful completion of the class, students even become certified green belts.

One item we talked about was how valuable the experiential component of the projects can be for students, especially...

Expanding the Role of Statistics to Areas Traditionally Dominated by Expert Judgment

Should this doctor consult a regression model?

In a previous post, I wrote about how the field of statistics is more important now than ever before due to the modern deluge of data. Because you’re reading Minitab's statistical blog, I’ll assume that we’re in agreement that statistics allows you to use data to understand reality. However, I’d also bet that you’re picturing important but “typical” statistical studies, such as studies where Six Sigma analysts determine which factors affect product quality. Or perhaps medical studies, like determining the effectiveness of flu shots.

In this post,...

How to “Expand” Your Gage Studies

As we said in yesterday’s post, it’s been exciting for Minitab to be a supporter of the ASQ World Conference on Quality and Improvement taking place this week in Indianapolis. There have been many great sessions and an abundance of case studies shared that highlight how quality teams worldwide are improving the performance of their businesses.

One session that generated a lot of interest from the conference participants was conducted by Minitab trainers Lou Johnson, Daniel Griffith and Jim Colton.

Their presentation, Sampling Plan for Expanded Gage R&R Studies, covered Gage R&R studies and how...