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Michelle Paret

I love statistics so much that I earned both my undergrad and graduate degrees on the subject. (I'm an outlier, I know.) My blog lets me share some of what I’ve learned with you! Continue Reading »

You run a capability analysis and your Cpk is bad. Now what? First, let’s start by defining what “bad” is. In simple terms, the smaller the Cpk, the more defects you have. So the larger your Cpk is, the better. Many practitioners use a Cpk of 1.33 as the gold standard, so we’ll treat that as the gold standard here, too. Suppose we collect some data and run a capability analysis using Minitab Statisti... Continue Reading
Rare events inherently occur in all kinds of processes. In hospitals, there are medication errors, infections, patient falls, ventilator-associated pneumonias, and other rare, adverse events that cause prolonged hospital stays and increase healthcare costs.  But rare events happen in many other contexts, too. Software developers may need to track errors in lines of programming code, or a quality... Continue Reading

7 Deadly Statistical Sins Even the Experts Make

Do you know how to avoid them?

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We like to host webinars, and our customers and prospects like to attend them. But when our webinar vendor moved from a pay-per-person pricing model to a pay-per-webinar pricing model, we wanted to find out how to maximize registrations and thereby minimize our costs. We collected webinar data on the following variables: Webinar topic Day of week Time of day – 11 a.m. or 2 p.m. Newsletter promotion –... Continue Reading
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... Continue Reading
"Do it myself!” If only I had a nickel for every time I heard that phrase from my toddler in a given day. From throwing away trash, to putting frozen waffles in the toaster, to feeding the dog, I hear it so often that I could possibly retire with all the nickels I’d collect. And of course, I hear this proclamation every single time my 2-year-old puts on her shoes. What happens when a toddler tries to... Continue Reading
When I think about the Central Limit Theorem (CLT), bunnies and dragons are just about the last things that come to mind. However, that’s not the case for Shuyi Chiou, whose playful CreatureCast.org animation explains the CLT using both fluffy and fire-breathing creatures. Per the article that accompanied this video in The New York Times: “Many real-world observations can be approximated by, and... Continue Reading
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... Continue Reading
In my last post, I used U.S. Census Bureau data and correlation to reveal that people living in colder, more crowded states typically make more money. I’m sure there is some rationale to support this conclusion, but I’ll leave that explanation up to the economists. Meanwhile, let's you and me move on to more statistics… Once I discovered there was correlation between income and other census data,... Continue Reading
I recently read an article about how the United States median household income has declined the last two years in a row. While that should make most of us as joyful as a vegetarian who just won a lifetime supply of beef jerky, there are some states that have median household incomes well above the norm. So, any guesses as to which state is the best at over $70K, and which is the worst at nearly... Continue Reading
Trying to remember what the alpha-level, p-value, and confidence interval all mean for a hypothesis test—and how they relate to one another—can seem about as daunting as Dorothy’s trek down the yellow brick road. Rather than sitting through a semester of Intro Stats, let's get right to the point and explain in clear language what all these statistical terms mean and how they relate to one another. Wh... Continue Reading
A statistician walks into a party. The host looks up and says “Welcome! Let me introduce you to everyone. This is John, Jeff, Jill, another Jeff, Petra, Porter, Paxtyn and Chris.” The statistician declares, “I love parties that exhibit properties of the Pareto principle!” The host—not a statistician—slowly turns and walks away, befuddled and bewildered. True story? Almost, except I kept inner... Continue Reading
If you're one of the gazillion people who have read The Hunger Games, then you’re quite familiar with “Real or Not Real?” And if you haven't read it, I'm guessing you've at least heard about this best-selling trilogy. The Hunger Games movie, like the book, has been a huge success, grossing over $400 million domestically. I recently saw an ad for the DVD to be released on August 18 and it got me... Continue Reading
I couldn’t wait to get to the Guinness brewery after landing in Dublin. Yes, I was eager to taste a pint nearly fresh off the line, but I was also curious to see if there would be any indication that the brewery was home to arguably one of THE most important developments in the field of statistics. I was not disappointed. There on the wall in the old Guinness Storehouse was a lone plaque paying... Continue Reading
In my last post, I talked about the danger of excluding interactions between factors in ANOVA and DOE models. Let’s now look at what can happen if you exclude an important factor altogether. Warning: misleading high p-value up ahead... Minitab regularly hosts webinarson different statistical topics. Let’s suppose we want to evaluate if certain webinar topics are more popular than others, so we... Continue Reading
Do you prefer ketchup or soy sauce? If someone asked you this question, your answer would likely depend upon what you were eating. You probably wouldn't dunk your spicy tuna roll in ketchup. And most people (pregnant moms-to-be excluded) don't seem to fancy eating soy sauce with hot French fries. A Common Error When Using ANOVA or DOE to Assess Factors Modeling techniques such as ANOVA or Design of... Continue Reading
We always hear about the "average" of this and the "average" of that…the average temperature, the average price of gasoline, the average number of children per household, etc.  In fact, I just saw an article on average student math scores by country. If you're a college grad, take a minute to recall when you were choosing your major. For those of us with aspirations of making big bucks, studying to... Continue Reading
I love the field of statistics. It gives us the ability to remove human bias and opinion to discern between what is truly important - and significant - from those things that are not. For instance, have you ever been at a meeting where a time series plot is displayed up on the screen and someone declares there is a spike in the data? Well, according to what? Let's use the power of statistics and... Continue Reading
Variation is everywhere. It’s in your daily commute to work, it’s in the amount of caffeine you drink every day, in the number of e-mails that arrive in your inbox, etc. Whether you’re monitoring something as ordinary as caffeine consumption or something more important like a multi-million dollar manufacturing process, you can use one simple tool to monitor variation and determine whether the... Continue Reading
Happy Groundhog Day! For those of you who are not familiar with this crazy American holiday (or have yet to see the Bill Murray movie by the same name), every year on February 2nd thousands of excited onlookers gather in a small Pennsylvania town named Punxsutawney to find out if spring will come early or if we’ll have to wait another dreaded 6 weeks for winter to end.And how do we learn what the... Continue Reading