Blog posts and articles about statistical principles in quality improvement methods like Lean and Six Sigma.

If you’re in the market for statistical software, there are many
considerations and more than a few options for you to evaluate.
Check out these seven questions to ask yourself before choosing
statistical software—your answers should help guide you towards the
best solution for your needs!
1. Who uses statistical software in your organization?
Are they expert statisticians, novices, or a mix of both?... Continue Reading

In 2011 we had solar panels fitted on our property. In the last
few months we have noticed a few problems with the inverter (the
equipment that converts the electricity generated by the panels
from DC to AC, and manages the transfer of unused electric to the
power company). It was shutting down at various times throughout
the day, typically when it was very sunny, resulting in no
electricity being... Continue Reading

In regression, "sums of squares" are used to represent
variation. In this post, we’ll use some sample data to walk through
these calculations.
The
sample data used in this post is available within Minitab by
choosing Help > Sample Data,
or File > Open Worksheet >
Look in Minitab Sample Data folder (depending on
your version of Minitab). The dataset is called
ResearcherSalary.MTW, and contains data... Continue Reading

So the data you nurtured, that you worked so hard to format and
make useful, failed the normality test.
Time to face the truth: despite your best efforts, that data set
is never going to measure up to the assumption you may
have been trained to fervently look for.
Your data's lack of normality seems to make it poorly suited for
analysis. Now what?
Take it easy. Don't get uptight. Just let your data... Continue Reading

See if this
sounds fair to you. I flip a coin.
Heads: You win
$1.Tails: You pay me $1.
You may not like games of chance, but you have to admit it seems
like a fair game. At least, assuming the coin is a normal, balanced
coin, and assuming I’m not a sleight-of-hand magician who can
control the coin.
How about this next
game?
You pay me $2 to play.I flip a coin over and over until
it comes up heads.Your... Continue Reading

I thought 3
posts would capture all the thoughts I had about B10 Life. That is,
until this question appeared on the Minitab LinkedIn
group:
In case you missed it, my first post,
How to Calculate B10 Life with Statistical Software, explains
what B10 life is and how Minitab calculates this value. My second
post,
How to Calculate BX Life, Part 2, shows how to compute any BX
life in Minitab. But... Continue Reading

The Centers for Medicare and Medicaid Services (CMS) updated
their star ratings on July 27. Turns out, the list of hospitals
provide a great way to look at how easy it is to get random samples
from data within Minitab.
Say for example, that you wanted to look at the association
between the government’s new star ratings and the safety rating
scores provided by hospitalsafetyscore.org. The CMS score... Continue Reading

Back
when I used to work in Minitab Tech Support, customers often asked
me, “What’s the difference between Cpk and Ppk?” It’s a good
question, especially since many practitioners default to using Cpk
while overlooking Ppk altogether. It’s like the '80s pop
duo Wham!, where Cpk is George Michael and Ppk is that other
guy.
Poofy hairdos styled with mousse, shoulder pads, and leg warmers
aside, let’s... Continue Reading

Figures lie, so they say, and liars figure. A recent post at Ben
Orlin's always-amusing mathwithbaddrawings.com blog nicely
encapsulates why so many people feel wary about anything
related to statistics and data analysis. Do take a moment to check it out, it's a fast
read.
In
all of the scenarios Orlin offers in his post, the statistical
statements are completely accurate, but the person offering... Continue Reading

Often, when we start analyzing
new data, one of the very first things we look at is whether
certain pairs of variables are correlated. Correlation can tell if two variables have a
linear relationship, and the strength of that
relationship. This
makes sense as a starting point, since we're usually looking for
relationships and correlation is an easy way to get a quick handle
on the data set we're... Continue Reading

The Olympic
games are about to begin in Rio de Janeiro. Over the next 16 days,
more than 11,000 athletes from 206 countries will be competing in
306 different events. That's the most events ever in any Olympic
games. It's almost twice as many events as there were 50 years ago,
and exactly three times as many as there were 100 years ago.
Since the number of Olympic events has changed over time,... Continue Reading

My recent beach vacation began with the kind of unfortunate
incident that we all dread: killing a distant relative.
It was about 3 a.m. Me, my two sons, and our dog had been on the
road since about 7 p.m. the previous day to get to our beach house
on Plum Island, Massachusetts. Google maps said our exit was coming
up and that we were only about 15 minutes away from our palace.
Buoyed by that... Continue Reading

Have you ever accidentally done statistics? Not all of us can
(or would want to) be “stat nerds,” but the word “statistics”
shouldn’t be scary. In fact, we all analyze things that happen to
us every day. Sometimes we don’t realize that we are compiling data
and analyzing it, but that’s exactly what we are doing. Yes, there
are advanced statistical concepts that can be difficult to
understand—but... Continue Reading

Statistics is all about modelling. But that doesn’t mean strutting down the
catwalk with a pouty expression.
It means we’re often looking for a mathematical form that best
describes relationships between variables in a population, which we
can then use to estimate or predict data values, based on known
probability distributions.
To aid in the search and selection of a “top model,” we often
utilize... Continue Reading

While some posts in our Minitab blog focus on
understanding t-tests and t-distributions this post will focus
more simply on how to hand-calculate the t-value for a one-sample
t-test (and how to replicate the p-value that Minitab gives
us).
The formulas used in this post are available within Minitab
Statistical Software by choosing the following menu path:
Help > Methods and Formulas
> Basic... Continue Reading

When I blogged about
automation back in March, I made my husband out to be an
automation guru. Well, he certainly is. But what you don’t know
about my husband is that while he loves to automate everything in
his life, sometimes he drops the ball. He’s human; even I have to
cut him a break every now and then.
On the other hand, instances of hypocrisy in his behavior tend
to make for a good story.... Continue Reading

You need to consider many factors when you’re buying a used car.
Once you narrow your choice down to a particular car model, you can
get a wealth of information about individual cars on the market
through the Internet. How do you navigate through it all to find
the best deal? By analyzing the data you have available.
Let's look at how this works using
the Assistant in Minitab 17. With the... Continue Reading

Here is a scenario involving process capability that we’ve seen
from time to time in Minitab's technical support department. I’m
sharing the details in this post so that you’ll know where to look
if you encounter a similar situation.
You need to run a capability analysis. You generate the output
using Minitab
Statistical Software. When you look at the results, the Cpk is
huge and the histogram in... Continue Reading

If you've used our software, you’re probably used to
many of the things you can do in Minitab once you’ve fit a
model. For example, after you fit a response to a given model for
some predictors with Stat > DOE > Response Surface
> Analyze Response Surface Design, you can do the
following:
Predict the mean value of the response variable for new
combinations of settings of the predictors.
Draw... Continue Reading

Design of Experiments (DOE) is the perfect tool to efficiently
determine if key inputs are related to key outputs. Behind the
scenes, DOE is simply a regression analysis. What’s not simple,
however, is all of the choices you have to make when planning your
experiment. What X’s should you test? What ranges should you select
for your X’s? How many replicates should you use? Do you need
center... Continue Reading