## Why the Weibull Distribution Is Always Welcome

In college I had a friend who could go anywhere and fit right in. He'd have lunch with a group of professors, then play hacky-sack with the hippies in the park, and later that evening he'd hang out with the local bikers at the toughest bar in the city. Next day he'd play pickup football with the jocks before going to an all-night LAN party with his gamer pals. On an average weekend he might catch an all-ages show with the small group of straight-edge punk rockers on our campus, or else check out a kegger with some townies, then finish the weekend by playing some D&D with his friends from the...

## Using Data Analysis to Assess Fatality Rates in Star Trek: The Original Series

I’m a Star Trek fan and a statistics fan. So, I’m thrilled to finally have the opportunity to combine the two into a blog post! In the original Star Trek series with Captain Kirk, the crew members of the U.S.S. Enterprise who wear red shirts have a reputation for dying more frequently than those who wear blue or gold shirts. Wearing a red shirt appears to be the kiss of death! In this blog, we’ll conduct several hypothesis tests to determine whether this is true.

Matthew Barsalou published an article in Significance that studies this from a statistical perspective. Barsalou is also a guest...

## How to Win an Oscar (If You Misunderstand Statistics)

Statistician-to-the-Stars William Briggs deserves credit for his correct prediction of the Best Picture Oscar the day before the ceremonies. And while Mr. Briggs would never encourage anyone to misuse his model this way, I feel my statistics heartstrings strummed by the desire to remind everyone about a particular common and dangerous statistical mistake: Correlation does not = causation.

Mr. Briggs correctly predicted Argo would be selected as Best Picture from among the nominated films and noted that  "The key reasons for its victory will be: the lead actor is at least forty, the other...

## My Work in Statistics: Developing New Tools for Analyzing Data

In honor of the International Year of Statistics, I interviewed Scott Pammer, a technical product manager here at Minitab Inc. in State College, Pa. Scott works to develop new product concepts and the accompanying prototypes and business plans.

Before taking on the role of technical product manager, Scott worked for Minitab as a senior statistician. In this role, he designed and programmed various features in Minitab Statistical Software. He’s been with Minitab since 1995.

## What was your journey to becoming a statistician?

When I was a senior in high school, I knew I needed to pick a college...

## What Makes Great Presidents and Good Models?

If the title of this post made you think you’d be reading about Abraham Lincoln and Tyra Banks, you’re only half right.

A few weeks ago, statistician and journalist Nate Silver published an interesting post  on how U.S. presidents are ranked by historians. Silver showed that the percentage of electoral votes that a U.S. president receives in his 2nd term election serves as a rough predictor of his average ranking of greatness.

Here’s the model he came up with, which I’ve duplicated in Minitab using the scatterplot with regression and groups (Graph > Scatterplot ):

Silver divided the data into...

## Basketball Statistics Question: How Important Is a Team's "Momentum" Heading into the NCAA Tournament?

It’s March, which means it’s the time of year when the country's sports fans focus their gaze upon college basketball. And since there are still a few weeks until the brackets come out, people will be trying to determine which teams are poised for a deep run in the tournament. One of the criteria people use to determine a team's potential is “momentum.” Everybody says you want your team to be “peaking at the right time.” But is this really important? We just saw the Baltimore Ravens win the Super Bowl despite losing 4 of their final 5 regular-season games.

So how important is it for NCAA...

## Helping Beginners Learn about Process Variation using Miles Per Gallon

by Robb Richardson, guest blogger

One of the things that I love most about my job is that I get to help educate, coach, and develop others on topics such as continuous improvement and data analysis.

In that capacity, one of the most frequently seen challenges is that team members and managers want to react to every data point. Their intentions are noble – but doing so is almost always an unnecessary exercise since these variations are a normal part of how the process behaves.

I’ve used lots of different examples to illustrate this point, but few seemed to resonate deeply with them and get them...

## Forget Statistical Assumptions - Just Check the Requirements!

One of the most poorly understood concepts in the use of statistics is the idea of assumptions. You've probably encountered many of these assumptions, such as "data normality is an assumption of the 1-sample t-test."  But if you read that statement and believe normality is a requirement of the 1-sample t-test, then you have missed a subtle and important characteristic of assumptions and need to read on...

## An "assumption" is not necessarily a "requirement"!

To understand where this idea of assumptions come from, let's forget about statistics for a minute and imagine we sell bikes online.  We...

## For Want of an FMEA, the Empire Fell

by Matthew Barsalou, guest blogger

For want of a nail the shoe was lost,
For want of a shoe the horse was lost,
For want of a horse the rider was lost
For want of a rider the battle was lost
For want of a battle the kingdom was lost
And all for the want of a horseshoe nail. (Lowe, 1980, 50)

According to the old nursery rhyme, "For Want of a Nail," an entire kingdom was lost because of the lack of one nail for a horseshoe. The same could be said for the Galactic Empire in Star Wars. The Empire would not have fallen if the technicians who created the first Death Star had done a proper Failure Mode and...

## Lightsaber Capability Analysis: Is Our Process In Control?

In my last post, we talked about using statistical tools to identify the right distribution of our lightsaber manufacturing data. Now that we have our data in Minitab along with a specific distribution picked out, we can find out if we are dealing with an in-control process. If the process is not in control, the capability estimates will be incorrect. Thus, an extremely important (and often overlooked) aspect of Capability Analysis is to make sure our process in first in control. We can do this with a tool Minitab Statistical Software offers called the Capability Sixpack.TM

First, let’s go to S...

## Why Statistics Is Important

"There are three kinds of lies: lies, damned lies, and statistics."

I’m sure you’ve heard this most vile expression, which was popularized by Mark Twain among others. This dastardly phrase impugns the reputation of statistics. The implication is that statistics can bolster a weak argument, or that statistics can be used to prove anything.

I’ve had enough of this expression, and here’s the rebuttal! In fact, I’ll make the case that statistics is not the problem, but the solution!

## Mistakes Can Happen

First, let’s stipulate that an unscrupulous person canintentionally manipulate the results to favor...

## Where to find meteorites, the Pareto chart way

It’s an amazing thing when a mass of rock and iron streaks through space and enters Earth’s atmosphere. So naturally, the Chelyabinsk meteor has attracted a great deal of attention. We’re fascinated by the images and captivated by the stories. And, if you’re interested in statistical analysis, you start to wonder a little bit about meteorites.

The nice thing is that the Meteoritical Society has a large database with information about meteorites recovered on Earth. The database has over 50,000 records.

It’s particularly neat to see where people find meteorites with recoverable masses. A Pareto...

## 3 Common (and Dangerous!) Statistical Misconceptions

Have you ever been a victim of a statistical misconception that’s affected how you’ve interpreted your analysis? Like any field of study, statistics has some common misconceptions that can trip up even experienced statisticians. Here are a few common misconceptions to watch out for as you complete your analyses and interpret the results.

### Mistake #1: Misinterpreting Overlapping Confidence Intervals

When comparing multiple means, statistical practitioners are sometimes advised to compare the results from confidence intervals and determine whether the intervals overlap. When 95%...

## 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...

## Is This the Craziest College Basketball Season Ever?

The last few weeks have been pretty crazy in college basketball. In the first 13 days of February, nine different teams ranked in the Top 10 have lost. And had Duke not squeaked by Boston College last Sunday, it would have been the first time since 1992 that every team ranked in the AP Top 5 had lost in a single week.

All of this has led to analysts saying that the parity in college basketball is greater than it’s ever been. And while it might seem that way, it’s always best to perform a data analysis to confirm whether your claims are true. Have there really been more Top 10 upsets this year...

## Making Statistics Sweet on Valentine's Day

Planning on giving a bag of M&M's to your sweetie this Valentine's Day? Well, you can woo your Valentine with not only the gift of candy, but also the statistics behind those candy-coated chocolate pieces.

## Are there equal amounts of each color in a bag?

You can record your counts of each color in the bag in a Minitab worksheet, and then use a pie chart (Graph > Pie Chart) to visualize the counts:

There were 138 blue M&M’s and only 63 red M&M’s in our sample. But is the difference between these counts statistically significant? A Chi-square test can tell us:

The p-value of 0.000 suggests...

## A Story-based Approach to Learning Statistics (and Statistical Software)

Want to learn more about analyzing data? Try taking a page from Aesop's book.

Well...really, I'm suggesting taking multiple pages from Minitab's book, but my suggestion stems from an idea that Aesop epitomizes.

Aesop was no fool. When he wanted to convey even the heaviest of lessons, he didn't waste time detailing the intellectual and philosophical arguments behind them. He didn't argue, cajole, or berate. He didn't lecture or pontificate.

He told a story.

Minitab uses the same approach in Meet Minitab, the introductory guide to data analysis and quality statistics using our statistical...

## They Call Them "Free" Throws For a Reason

When Penn State guard Jermaine Marshall stepped to the line to take two free throws with 0:27 remaining against Ohio State, it didn’t really matter whether he made the shots. The game was already out of reach, and although the Nittany Lions would attempt to foul their way into a miracle victory, most of the fans were all too aware that Penn State was now 0-8.  That Marshall then missed both free throws was the exclamation point on a night where the team made just 13 of 22 free throw attempts.

Lest you not already know this, a "free throw" is a shot taken against no defense, a shot that likely...

## Flu Shot Followup: Assessing the Long-Term Benefits of Flu Vaccination

In my last post, I wrote about the 60% effectiveness rate for flu shots that news media commonly report. The effectiveness is actually a relative measure of the reduction in your flu risk if you’re vaccinated. Relative measures are hard to interpret without additional information. With that in mind, I reanalyzed the data to put it in absolute terms. I found that if you get a flu shot, your average annual risk of getting the flu drops from 7.0% to 1.9%, which is a 5.1% reduction.

I’ve received several requests to look at this over a longer timeframe. After all, flu shots aren’t a one-time thing....

## Violations of the Assumptions for Linear Regression: Residuals versus the Fits (Day 3)

Lionel Loosefit has been hauled to court for violating the assumptions of linear regression. On Day 3 of the trial, the court examines the allegation that the residuals in Mr. Loosefit's model exhibit nonconstant variance. The defendant’s mother, Mrs. Lottie Loosefit, has taken the stand on behalf of her son.

Defense Attorney: So, Mrs. Loosefit, from what you’ve described to us, your son, Lionel, appears to have been a model child.

Lottie Loosefit [eyes watering]: He was every mother’s dream. He brushed his teeth every morning and every night, made his bed, folded his socks, picked up all his...