# Patrick Runkel

Communicating statistical concepts quickly and clearly is just as critical as being able to calculate them, so I focus on quick, practical insights about statistics to help you make data-driven decisions. Continue Reading »

I always knew I was different. Even as a kid. “Is that me? Way out there in left field?” I asked the doc. “Yes,” he nodded, as he looked at my chart. “I used brushing to identify you on the graph.” I wasn’t sure I liked getting brushed. It felt like my true identify was being detected and displayed in a window for all to see. The doctor must have sensed my discomfort. “It’s not uncommon—even for those... Continue Reading
"He looks just like his father...and mother!" Popular morphing sites online let you visualize the hypothetical offspring of some very unlikely couples. The baby of Albert Einstein and Kim Kardashian (Kimbert?) would presumably look something like the image shown at right. What happens if you morph the features of two different graphs? For example, what would the baby of a time series plot and... Continue Reading

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The word kurtosis sounds like a painful, festering disease of the gums. But the term actually describes the shape of a data distribution. Frequently, you'll see kurtosis defined as how sharply "peaked" the data are. The three main types of kurtosis are shown below. Lepto means "thin" or "slender" in Greek. In leptokurtosis, the kurtosis value is high. Platy means "broad" or "flat"—as in duck-billed pl... Continue Reading
Do you suffer from PAAA (Post-Analysis Assumption Angst)? You’re not alone. Checking the required assumptions for a statistical  analysis is critical. But if you don’t have a Ph.D. in statistics, it can feel more complicated and confusing than the primary analysis itself. How does the cuckoo egg data, a common sample data set often used to teach analysis of variance, satisfy the following formal... Continue Reading
If you teach statistics or quality statistics, you’re probably already familiar with the cuckoo egg data set. The common cuckoo has decided that raising baby chicks is a stressful, thankless job. It has better things to do than fill the screeching, gaping maws of cuckoo chicks, day in and day out. So the mother cuckoo lays her eggs in the nests of other bird species. If the cuckoo egg is similar... Continue Reading
You know what really gets on my nerves? A lot of things. That slow, slinky way that cats walk by. Grrrr. The rude, abrupt arrival of delivery persons in their obnoxiously loud trucks. (Why do they always pull up just as I’m settling down for a nap?) Grrrr. Total strangers who reach down and poke me with fat, clumsy fingers that reek of antibacterial soap. Grrrr. And this one always gets my dander up:... Continue Reading
These days, my memory isn't what it used to be. Besides that, my memory isn't what it used to be.  But my incurable case of CRS (Can't Remember Stuff) is not nearly as bad as that of the exponential distribution. When modelling failure data for reliability analysis, the exponential distribution is completely memoryless. It retains no record of the previous failure of an item. That might sound like a... Continue Reading
A famous classical Chinese poem from the Song dynasty describes the views of a mist-covered mountain called Lushan. The poem was inscribed on the wall of a Buddhist monastery by Su Shi, a renowned poet, artist, and calligrapher of the 11th century. Deceptively simple, the poem captures the illusory nature of human perception.      Written on the Wall of West Forest Temple                               ... Continue Reading
My previous post examined how an equivalence test can shift the burden of proof when you perform hypothesis test of the means. This allows you to more rigorously test whether the process mean is equivalent to a target or to another mean. Here’s another key difference: To perform the analysis, an equivalence test requires that you first define, upfront, the size of a practically important difference... Continue Reading
With more options, come more decisions. With equivalence testing, 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... Continue Reading
Minitab Statistical Software includes a graphical analysis called the Bubble Plot. This exploratory tool is great for visualizing the relationships among three variables on a single plot. To see how it works, consider the total medal count by country from the recently completed 2014 Olympic Winter Games. Suppose I want to explore whether there might be a possible association between the number of... Continue Reading
What factors significantly affect how quickly my couch-potato pooch obeys the “Lay Down” command? The cushiness of the floor surface? The tone of voice used? The type of reward she gets? How hungry she is? I created a 1/8 fraction Resolution IV design for 7 factors and collected response data for 16 runs. Now it’s time to analyze the data in Minitab, using  Stat > DOE > Factorial > Analyze Factorial... Continue Reading
Nala, our 6-year-old golden retriever, loves her dogma. That's her sitting in front of church on Sunday morning. But she's not crazy about her catechism. For example, she doesn't always dutifully follow the "Lay Down" commandment.   What factors may be influencing her response? We're performing a DOE screening experiment to find out. In this post, we'll use Minitab Statistical Software to Create the... Continue Reading
Design of experiments (DOE) is an extremely practical and cost-effective way to study the effects of different factors and their interactions on a response. But finding your way through DOE-land can be daunting when you're just getting started. So I've enlisted the support of a friendly golden retriever as a guide dog to walk us through a simple DOE screening experiment. Nala, the golden retriever,... Continue Reading
What do you see when you look at the image at right? Do you see a bulging sphere that stretches the checkerboard pattern in the center, causing its lines to curve? Are you sure? Look again. This time, test any “curved” line by holding a straightedge next to it. The image is actually composed of small squares and straight lines. Yet, when perceived as a composite whole, it creates a completely... Continue Reading
Does the prospect of a looming U.S. government shutdown depress you? Are you tired of the ongoing game of Chicken played over our federal budget? The dissonant hysterics of deficit drama queens? The glib arrogance of deficit deniers? Then it might be a good time to take a break and focus on something more pleasant. Something you can control. Something you can improve and make more beautiful. Like... Continue Reading
Defects can cause a lot of pain to your customer. They can also cause a lot of pain inside your body. The picture at right shows my broken right clavicle. Ouch! You might think of it as the defective output from my bicycling process, which needs improvement. Sitting around all summer cinched up in a foam orthopedic brace hasn’t exactly been wild and wacky 50s-style fun at the beach. But the injury has... Continue Reading
It’s wildfire season out West. Time to be in awe of the destructive power of Nature. According to active fire maps by the USDA Forest Service, over 300 fires are now burning across a total of 1.5 million acres—including 35 large, uncontained blazes. Shifting winds, humidity, and terrain can quickly alter a fire's intensity. In extreme conditions, flames can reach over 150 feet, with temperatures... Continue Reading
True confession: Nothing fires quickly from the top of my head. At least nothing very lucid or useful. To come up with a good idea, I have to dredge thoughts slowly from the thick sludge and sediment in my brain.  It's not always easy—there are deeply encrusted layers in my cerebral cortex that go all the way back to the Paleozoic era. So coming up with a useful data display—one that uncovers hidden... Continue Reading
My Uncle Joe is always fantasizing about ways to outsmart Father Time. “Suppose you could reverse your aging process at some fixed point in your life,” he says to me, a crazed gleam in his eye. “So you could pick any age to turn the clock backwards and start aging in reverse. What age would you pick to try to maximize your life span?”   In other words, suppose you pick age 75. That means you’d... Continue Reading