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 »
The word kurtosis sounds like a painful, festering
disease of the gums. But the term actually describes the shape of a
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
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
cuckoo egg data, a common sample data set often used to teach
analysis of variance, satisfy the following
formal... Continue Reading
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
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.
And this one always gets my dander up:... Continue Reading
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
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
Written on the Wall of West Forest Temple
... Continue Reading
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
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... Continue Reading
n' begorrah, it's St. Patrick's Day today!
The day that we Americans lay claim to our Irish heritage by
doing all sorts of things that Irish people never do. Like dye your
hair green. Or tell everyone what percentage Irish you are.
Despite my given name, I'm only about 15% Irish. So my Irish
portion weighs about 25 pounds. It could be the portion that hangs
over my belt due to excess potatoes... Continue Reading
By popular demand, Release 17 of Minitab
Statistical Software comes with a new 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... Continue Reading
you regularly perform regression analysis, you know that
R2 is a statistic used to evaluate the fit of your
model. You may even know the standard definition of R2:
the percentage of variation in the response that is explained
by the model.
Fair enough. With Minitab Statistical Software doing all the heavy
lifting to calculate your R2 values, that may be all you
ever need to know.
But if you’re... Continue Reading
This close to
the holidays, it’s hard to stay focused on work.
I should be writing a post about useful estimation
tools for quality statistics. But all those yuletide carols about
hosts of angels singing from on high have distracted me.
Alas, I’ve fallen into the clutches of one of the world’s oldest
estimation problems, posed centuries ago by medieval scholars:
Just how many heavenly angels can... Continue Reading
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
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
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
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
But the injury has... Continue Reading
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
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
Minitab is the leading provider of software and services for quality
improvement and statistics education. More than 90% of Fortune 100 companies
use Minitab Statistical Software, our flagship product, and more students
worldwide have used Minitab to learn statistics than any other package.
Minitab Inc. is a privately owned company headquartered in State College,
Pennsylvania, with subsidiaries in the United Kingdom, France, and
Australia. Our global network of representatives serves more than 40
countries around the world.