## Violations of the Assumptions for Linear Regression: Closing Arguments and Verdict

Lionel Loosefit has been hauled to court for violating the assumptions of regression analysis. On the last day of the trial, the prosecution and defense present their closing arguments. And the fate of Mr. Loosefit is decided by judge and jury...

## The Prosecution's Summary

Prosecutor: Ladies and gentlemen, we’ve presented a slew of evidence in this trial. You’ve seen, with your own eyes, every possible heinous violation of the assumptions for regression in the defendant’s model. Here’s what we’ve shown, in a nutshell:

Prosecutor: We’ve carefully delineated each violation with specific graphic...

## The Best Super Bowl Commercials of 2013, Plotted in Minitab

Various commercials valiantly vied for the attention and dollars of football Super Bowl commercial fans on Sunday. The game was decided objectively (or by the referees), but the drama of which commercials won lives on. Because we love data analysis, I gathered a little bit to see which efforts really stood out. Then I plotted the data in Minitab to explore the results.

Three top-ten lists attracted my attention:

## A Simple Guide to Gage R&R for Destructive Testing

Measurement systems analysis (MSA) is essential to the success of any data analysis. If you cannot rely on the tool you’re using to take measurements, then why bother collecting data to begin with? It would be like trying to lose weight while relying on a scale that doesn’t work. What’s the point in weighing yourself?

Minitab Statistical Software offers many types of tools that you can use to assess your measurement system, including:

• Gage R&R Study (Crossed)
• Gage R&R Study (Nested)
• Attribute Agreement Analysis

## Destructive Testing Defined

In MSA studies for continuous measurements (e.g. weight,...

## Violations of the Assumptions for Linear Regression (Day 2): Independence of the Residuals

Recap: Lionel Loosefit has been arrested and hauled to court for violating the assumptions of regression analysis. In the previous court session, the prosecution presented evidence to show that the errors in Mr. Loosefit’s model were not normally distributed. Today, the prosecution addresses the second alleged violation: namely, that the errors in the defendant’s regression model are not independent. Dr. Minnie Tabber, a world-renowned statistician, is on the witness stand.

Prosecutor: Let me remind the members of the jury that a residual is simply the difference between the data value...

## Lightsaber Capability Analysis: Picking the Right Distribution

In my previous post, you learned how to prepare your data for capability analysis in Minitab. Now let's see where we need to go in the statistical software to run the correct Capability Analysis.

When it comes to capability analysis, Minitab offers a few different choices. We offer Normal Capability Analysis for when your data follow a normal distribution. If your data follow a different distribution, such as the Weibull distribution, there's Non-normal Capability Analysis. We also offer Binomial Capability and Poisson Capability for when you are looking to produce a process capability report...

## FMEA: A Good Way to Save Yourself Some Grief

In the past couple of years, I've noticed a new acronym popping up across the Web. In case you've not yet encountered it, "FML" typically appears in social media updates about something gone awry.  As in, "The cat ate my homework. FML!"  Or, "My production line just broke down, and now the company is going to be short on a major order. FML!"

This acronym reminds me of an abbreviation used in Lean Six Sigma and quality improvement: FMEA.  It's short for "Failure Modes and Effects Analysis," which basically means "look very, very carefully at how and why stuff can go wrong."

## Don't Forget to Look at How You Collect Data (Whether You're Hunting Quality or Ghosts)!

by Matthew Barsalou, guest blogger

In Jim Frost’s article “How to Be a Ghost Hunter with a Statistical Mindset,” he correctly pointed out the difficulties in distinguishing small effects from natural variation. However, he did not mention the benefits of doing measurement system analysis (MSA) in both ghost hunting as depicted by his example and in the statistical study using Minitab.

In industrial settings, testing equipment is evaluated to determine if the device used to assess the factor being studied is taking accurate measurements. In other words, are you collecting data that you can...

## Two-Tip Tuesday: Setting Default Options in Minitab Statistical Software

If you’re looking to save some time while using Minitab Statistical Software, check out these tips for setting default options.

## What Are the Options in My Statistical Software?

Options are default Minitab settings that you use each time that you create a graph or conduct an analysis. Some options are global in nature (What color would you like your graphs to be?), while others pertain only to certain graphs or tests (What tests should I perform when I create control charts?).

Some options have the effect of selecting items for you as you create a graph or perform an analysis, thereby saving you...

## Violations of the Assumptions for Linear Regression: The Trial of Lionel Loosefit (Day 1)

Bailiff: All Rise. The Honorable Judge Lynn E. R. Peramutter presiding.

Bailiff: Your honor, this is the case of the State vs. Lionel Loosefit. The defendant is charged with creating a model that violated the legal requirements for regression. The infractions include:

• Producing grossly nonnormal errors
• Producing errors that lack independence
• Exhibiting nonconstant variance
• Violating the linearity assumption

Judge: Thank you, bailiff. Let’s hear the opening statement by the prosecutor.

## Choosing the Right Distribution Model for Reliability Data

Recently I've been refreshing my knowledge of reliability analysis, which is the use of data to assess a product's ability to perform over time. Quality engineers typically use reliability analysis to predict the likelihood that a certain percentage of products will fail over a given amount of time.

Statistical software will do the calculations involved in a reliability analysis, but there's a catch: first, you must choose a distribution to model your data. Put plainly, you need to tell the software to base its analysis on the normal distribution, the Weibull distribution, or perhaps some...

## How I Came to Grips with Statistics in Manufacturing

The Minitab Fan section of the Minitab blog is your chance to share with our readers! We always love to hear how you are using Minitab products for quality improvement projects, Lean Six Sigma initiatives, research and data analysis, and more. If our software has helped you, please share your Minitab story, too!

Growing up, I had little or no interest in math. In Africa we had little or no manufacturing; therefore, I had no idea about manufacturing processes, quality improvement, and so on. There was nothing there to motivate me play with numbers. I used to be terrified to see charts and...

## Holiday Baking: Using DOE to Bake a Better Cookie

It’s the most wonderful time of the year – the time for holiday bakers and cookie monsters to unite! So what’s a quality improvement professional to do when his favorite sugar cookie recipe produced cookies that failed to hold their festive holiday shapes after being baked? Run a Design of Experiment (DOE), of course!

## A Fractional Factorial Experiment

Bill Howell, an avid baker and quality professional, used Minitab’s DOE tools to get to the bottom of his sugar cookie shape faux pas.

Howell planned to design an experiment that would allow him to screen many factors, determine which were most...

## Using Statistics for Process Improvement Outside of Manufacturing

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 industry segments, such as healthcare and banking, also rely on data analysis and Lean Six Sigma tools to improve processes (even if those processes are more service-based).

For example, it’s increasingly common for healthcare professionals to conduct projects to help them investigate and understand certain clinical outcomes for patients, such as the incidence of a certain disease developing after...

## My Work with Minitab

The Minitab Fan section of the Minitab blog is your chance to share with our readers! We always love to hear how you are using Minitab products for quality improvement projects, Lean Six Sigma initiatives, research and data analysis, and more. If our software has helped you, please share your Minitab story, too!

Throughout my 15 years as a Six Sigma Initiative Leader, Consultant, Trainer, Black Belt and master Black Belt I have been enthusiastic about Minitab Statistical Software, starting from release 11 to now.

Minitab's graphics are outstanding in their ability to present messages and...

## Attending the Preliminary Round Judging of the ITEA

We got the opportunity a few weeks back to sit in on one of the preliminary round judging events that make up ASQ’s International Team Excellence Award Process (ITEA). I wrote about the ITEA in a previous post, but the process is an annual event that celebrates the accomplishments of quality improvement teams from a broad spectrum of industries.

Estonand I traveled to Charlotte, N.C., to attend the first of seven rounds of preliminary judging that take place each year throughout October and early November. Judges working in the quality improvement field from around the world are selected by...

## Managing Diabetes with Six Sigma and Statistics, Part II

In my last post, I discussed how quality professional Bill Howell chose to manage his diabetes diagnosis by treating it as a Six Sigma project. Since a key metric in controlling his disease was keeping his blood glucose levels below 125 mg/dL, he tested his blood using a meter three times per day and then charted his data to see how his levels changed over time. He ensured his measurement systems were producing reliable data, and assessed the potential causes for his increased blood glucose levels. He then chose to focus on the causes he could control and analyze himself.

## Statistics Is an Art

When you say the word "statistics" to people, most think about math. But not me. I think about art.   I was reminded about this when I received the following e-mail recently:  Hi Eston --

I read your paper on "Weather Forecasts: Just How Reliable Are They?" and have a few questions. I am a retired engineer who enjoys data and would like to do a similar study for my home town. I want to look at the NWS and our local TV stations' 7 day forecasts (high, lows and precip.).

I was wondering if you have more details on the statistical analysis. I did take statistics for engineers in college in...

## The Care and Feeding of Capital Equipment (with Reliability Statistics)

In industry, it may be presses and CNC machines. In education, it may be computers and microscopes. In retail, it may be the forklifts in the warehouse.

Regardless of your industry or the size of your business, in all likelihood you have one or more pieces of capital equipment that must be regularly maintained.  Typically these expensive pieces of equipment come with routine maintenance plans.  But what happens when, perhaps after a few years of running smoothly, the equipment starts showing signs of wear?  Perhaps it starts with just one small fix and all is well. Then it requires a few more...

## Managing Diabetes with Six Sigma and Statistics, Part I

According to the American Diabetes Association, nearly 26 million children and adults in the U.S. have diabetes, and another 79 million Americans are at risk for developing Type 2 Diabetes.

Type 2 Diabetes is the most common form of the disease, and it occurs when either the body does not produce enough insulin or the cells ignore the insulin. Insulin is important because it allows the body to use glucose (which the body makes by converting sugars and starches in foods) for energy, and it actually moves the sugar from the blood into the cells to be used. When glucose builds up in the...

## Why Do So Many U.S. Voters Go MIA on Election Day? (Part II)

So what stops eligible U.S. voters from showing up at the polls on election day?  I’m not going to be able to tease out all the possible factors associated with variability in voter turnout in one blog post.

But you can often be forgiven in statistics if you clearly state at the onset that your main objective is a preliminary exploration rather than a final, conclusive analysis. So let’s explore.

## Does temperature affect voter turnout?

Weather is sometimes suggested as a possible influence on voter turnout. Can you imagine the impact on the election if Hurricane Sandy had hit just one week later...