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...

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...

“Hello, How Can I Help You?”- A Look at Quality Improvement in Financial Services

It’s common to think that process improvement initiatives are meant to cater only to manufacturing processes, simply because manufacturing is where Lean and Six Sigma began. However, many other industries, in particular financial services and banking, also rely on data analysis and Lean Six Sigma tools to improve processes.

Rod Toro is a business process improvement manager at Edward Jones, and I recently got the chance to talk with him about a Lean Six Sigma project the service division at his company completed to improve customer satisfaction.

Edward Jones has been increasing the number of...

ITEA Sneak-Peek: The Great Escape from Foam Defects

The 2014 ASQ World Conference on Quality and Improvement is coming up in early May in Dallas, and this year’s International Team Excellence Award Process (ITEA) will also come to a close at the conference, as winners from the finalist teams will be chosen for ASQ gold, silver, or bronze-level statuses.

What’s ITEA?

The annual ASQ ITEA process celebrates the accomplishments of quality improvement teams from a broad spectrum of industries from around the world. The ITEA is the only international team recognition process of its kind in the United States, and since 1985, more than 1,000 teams from...

Equivalence Testing for Quality Analysis (Part I): What are You Trying to Prove?

With more options, come more decisions.

With equivalence testing added to Minitab 17, you now have more statistical tools to test a sample mean against target value or another sample mean.

Equivalence testing is extensively used in the biomedical field. Pharmaceutical manufacturers often need to test whether the biological activity of a generic drug is equivalent to that of a brand name drug that has already been through the regulatory approval process.

But in the field of quality improvement, why might you want to use an equivalence test instead of a standard t-test?

Interpreting Hypothesis...

The Best European Football League: What the CTQ’s and Minitab Can Tell Us

by Laerte de Araujo Lima, guest blogger

In a previous post (How Data Analysis Can Help Us Predict This Year's Champions League), I shared how I used Minitab Statistical Software to predict the 2013-2014 season of the UEFA Champions league. This involved the regression analysis of main critical-to-quality (CTQ) factors, which I identified using the “voice of the customer” suggestions of some friends.

Since that post was published, my friends have stopped discussing the UEFA Champions league—they were convinced by the results I shared.

But now they’ve challenged me to use Six Sigma tools to...

Control Chart Tutorials and Examples

The other day I was talking with a friend about control charts, and I wanted to share an example one of my colleagues wrote on the Minitab Blog.  Looking back through the index for "control charts" reminded me just how much material we've published on this topic.

Whether you're just getting started with control charts, or you're an old hand at statistical process control, you'll find some valuable information and food for thought in our control-chart related posts. 

Different Types of Control Charts

One of the first things you learn in statistics is that when it comes to data, there's no...

Using Statistics to Show Your Boss Process Improvements

Ughhh... your process is producing some parts that don't meet your customer's specifications! Fortunately, after a little hard work, you find a way to improve the process.

However, you want to perform the appropriate statistical analysis to back up your findings and make it easier to explain the process improvements to your boss. And it's important to remember that your boss is much like the boss in Eston's posts -- he's not too familiar with statistics, so you'll have to take it slow and show lots of "visual aids" in your explanation. How should you begin? 

Enter before-and-after process...

Got Good Judgment? Prove It with Attribute Agreement Analysis

Many Six Sigma and quality improvement tools could be applied in other areas. For example, I wonder whether my son's teachers could benefit from a little attribute agreement analysis. 

He seemed frustrated the other day when I picked him up at school. He'd been working on a presentation that needed to be approved by his teachers. (My son attends a charter school, and each class is taught by a two-person teaching team.)

"What's wrong?" I asked when he clambered into the car with a big sigh.

My son explained that he'd given the presentation to teacher Jennifer that morning. A few minor suggestions...

Say "I Love You" with Data on Valentine's Day

When we think about jobs with a romantic edge to them, most of us probably think of professions that involve action or danger.  Spies, soldiers, cops, criminals -- these are types of professions romantic leads have. Along with your occasional musician, reporter, or artist, who don't have the action but at least bring drama.

But you know who never shows up as a romantic lead?  Quality improvement professionals, that's who.  Can you name just one movie that features a dedicated data analyst or quality practitioner as the love interest...just one?  No, you can't.  Doesn't exist.

Love of Quality:...

Gauging Gage Part 1: Is 10 Parts Enough?

"You take 10 parts and have 3 operators measure each 2 times."

This standard approach to a Gage R&R experiment is so common, so accepted, so ubiquitous that few people ever question whether it is effective.  Obviously one could look at whether 3 is an adequate number of operators or 2 an adequate number of replicates, but in this first of a series of posts about "Gauging Gage," I want to look at 10.  Just 10 parts.  How accurately can you assess your measurement system with 10 parts?

Assessing a Measurement System with 10 Parts

I'm going to use a simple scenario as an example.  I'm going to...

Lessons in Quality During a Long and Strange Journey Home

I didn’t expect that our family trip to Florida would end with me driving a plane load of passengers nearly 200 miles to their homes, but it did.

Yes, it was a long and strange journey home. A journey that started in the tropical warmth of southern Florida and ended the next morning in central Pennsylvania, which felt like the arctic wastelands thanks to the dreaded polar vortex.

During this journey, I didn’t just experience temperature extremes, but also extremely different levels in the quality of customer care. Working at Minitab, I'm very aware of the quality of service because quality...

Setting the Stage: Accounting for Process Changes in a Control Chart

When looking at a control chart, it’s important to know that the data we are looking at is accurate. Let’s face it, if the control limits we are looking at don’t really reflect what’s actually happening in our process, what does it matter if our points fall within the limits, or a little bit outside?

Let’s take a trip down to the widget factory, where widgets are being produced in all shapes and sizes. We’re going to take a look at one particular widget, and the time it takes for that particular widget to be produced (in minutes).

In a Minitab Statistical Software datasheet, we have two months...

Applying Six Sigma to a Small Operation, Part 2

In my previous post, I shared a case study of how a small bicycle-chain manufacturing company in India used the DMAIC approach to Six Sigma to reverse declining productivity.

After completing the Define, Measure, and Analysis phases, the team had identified the important factors in the bushing creation process. Armed with this knowledge, they were now ready to make some improvements.

The Improve Phase

In the Improve phase, the team applied a statistical method called Design of Experiments (DOE) to optimize the important factors they'd identified in the initial phases.

Most of us learn in school...

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...

Creating a Shatterproof Process: Students Use Six Sigma to Improve Window Manufacturing

I had the opportunity to speak with a great group of students from the New Jersey Governor’s School of Engineering and Technology—a summer program for high-achieving high school students. Students in the program complete a set of challenging courses while working in small groups on real-world research and design projects that relate to the field of engineering. Governor’s School students are mentored by professional engineers as well as Rutgers University honors students and professors, and they often work with companies and organizations to solve real engineering problems.

The team of students...

The Value Stream Map: It's Been Around Longer than You Think

In looking for the answer to an unrelated quality improvement question the other day, I ran across a blog post that answers a question I'd had for a while: what's the origin of the value stream map? 

A value stream map (VSM) is a key tool in many quality improvement projects, especially those using Lean. The value stream is the collection of all of the activities, both value-added and non-value added, that generate a product or service that meets customer needs. The VSM shows how both materials andinformation flow as a product or service moves through the process value stream, helping teams...

Avoiding a Lean Six Sigma Project Failure, part 4

In my first post in this series, I mentioned that we reached out to our customers who are practitioners in the field of quality improvement to better understand how they complete projects, what tools they use, and the challenges and roadblocks they come across in achieving success with quality initiatives. One area quality leaders said they were struggling with was the training aspect of their programs—actually getting their belts and/or project team members up to speed with adequate training to complete projects independently.

Insufficient Training

They told us projects were failing because of...

Understanding ANOVA by Looking at Your Household Budget

by Arun Kumar, guest blogger

One of the most commonly used statistical methods is ANOVA, short for “Analysis of Variance.” Whether you’re analysing data for Six-Sigma styled quality improvement projects, or perhaps just taking your first statistics course, a good understanding of how this technique works is important.

A lot of concepts are involved in any analysis using ANOVA and its subsequent interpretation. You’re going to have to grapple with terms such as Sources of Variation, Sum of Squares, Mean Squares, Degrees of Freedom, and F-ratio—and you’ll need to understand what statistical...