Blog posts and articles with tips for analyzing data for quality improvement methodologies, including Six Sigma and Lean.

True or false: When comparing a parameter for two sets of
measurements, you should always use a hypothesis test to determine
whether the difference is statistically significant.
The answer? (drumroll...) True!
...and False!
To understand this paradoxical answer, you need to keep in mind
the difference between samples, populations, and descriptive and
inferential statistics.
Descriptive Statistics and... Continue Reading

Data
mining uses algorithms to explore correlations in data sets. An
automated procedure sorts through large numbers of variables and
includes them in the model based on statistical significance alone.
No thought is given to whether the variables and the signs and
magnitudes of their coefficients make theoretical sense.
We tend to think of data mining in the context of big data, with
its huge... Continue Reading

Today,
September 16, is World Ozone Day. You don't hear much about the
ozone layer any more.
In fact, if you’re under 30, you might think this is just
another trivial, obscure observance, along the lines of International Dot Day (yesterday) or National Apple Dumpling Day (tomorrow).
But there’s a good reason that, almost 30 years ago, the United
Nations designated today to as a day to raise... Continue Reading

I confess: I'm not a natural-born decision-maker. Some people—my
wife, for example—can assess even very complex situations, consider
the options, and confidently choose a way forward. Me? I get
anxious about deciding what to eat for lunch. So you can imagine
what it used to be like when I
needed to confront a really big decision or problem. My approach,
to paraphrase the Byrds, was "Re:... Continue Reading

There may be huge potential benefits waiting in the data in your
servers. These data may be used for many different purposes. Better
data allows better decisions, of course. Banks, insurance firms,
and telecom companies already own a large amount of data about
their customers. These resources are useful for building a more
personal relationship with each customer.
Some organizations already use... 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

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

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