Blog posts and articles about using Minitab software in quality improvement projects, research, and more.

If you want to convince someone that at least a basic
understanding of statistics is an essential life skill, bring up
the case of Lucia de Berk. Hers is a story that's too awful to be
true—except that it is completely true.
A
flawed analysis irrevocably altered de Berk's life and kept her
behind bars for five years, and the fact that this analysis
targeted and harmed just one person makes it more... Continue Reading

When I wrote
How to Calculate B10 Life with Statistical
Software, I promised a
follow-up blog post that would describe how to compute any “BX”
lifetime. In this post I’ll follow through on that promise, and in
a third blog post in this series, I will explain why BX life is one
of the best measures you can use in your reliability
analysis.
As a refresher, B10 life refers to the time at which 10% of... Continue Reading

In this post, I’ll address some common questions we’ve received
in technical support about
the difference between fitted and data means, where to find each
option within Minitab, and how Minitab calculates each.
First,
let’s look at some definitions. It’s useful to have an example, so
I’ll be using the Light Output data set from Minitab’s Data Set
Library, which includes a description of the sample... Continue Reading

If
you follow the news in the United States then you’ve heard that
there’s a water crisis in Flint, Michigan. Although there’s going
to continue to be debate about how much ethics played a role in the
data collection practices, it’s worthwhile to at least be ready to
perform the correct analysis on the data when you have it. Here’s
how you can use Minitab to be like a citizen data scientist... Continue Reading

If you need to assess process
performance relative to some specification limit(s),
then process
capability is the tool to use. You collect some accurate
data from a stable process, enter those measurements in Minitab,
and then choose Stat > Quality Tools >
Capability Analysis/Sixpack or Assistant
> Capability Analysis.
Now, what about sorting the data?
I’ve been asked “why does Cpk change when I... Continue Reading

In the world of linear models, a hierarchical model contains all
lower-order terms that comprise the higher-order terms that also
appear in the model. For example, a model that includes the
interaction term A*B*C is hierarchical if it includes these terms:
A, B, C, A*B, A*C, and B*C.
Fitting the correct regression model can be as
much of an art as it is a science. Consequently, there's not always
a... Continue Reading

In my time at Minitab, I’ve gotten a good understanding of what
types of graphs users create. Everyone knows about histograms, bar
charts, and time series plots. Even relatively less familiar plots
like the interval plot and
individual value plot are still used quite often.
However, one of the most underutilized graphs we have available is
the area graph. If you’re not familiar with an Area... Continue Reading

Any time you see a process
changing, it's important to determine why. Is it indicative of a
long term trend, or is it a fad that you can ignore since it will
be gone shortly?
For example, in the 2014 NBA Finals, the San Antonio Spurs beat
the two-time defending champion Miami Heat by attempting more
3-pointers (23.6 per game) than any championship team in league
history. In the 2015 regular... Continue Reading

Unless you live under a black
country rock, you’ve no doubt heard that the world recently lost
one of the greatest artists of our time, David Bowie. My memories
of the Thin White Duke go all the way back to my formative years. I
recall his music echoing through the halls of our house as I
crooned along whilst doing the chores. Then as now, Bowie’s
creativity and energy inspired me and helped me do... Continue Reading

Ahh,
bottled water. Refreshing, convenient...and sometimes pricey. Or in
my case, I should say usually pricey. Confession: I’m a
sucker for water that comes in the “pretty” plastic bottles, and my
experience is that the pretty-bottle brands are usually the pricier
ones. Does bottled water cost increase with the fanciness of the
bottle? Well, that could be an analysis for a different day …
My... Continue Reading

How deeply has statistical content from Minitab blog posts (or
other sources) seeped into your brain tissue? Rather than submit a
biopsy specimen from your temporal lobe for analysis, take this
short quiz to find out. Each question may have more than one
correct answer. Good luck!
Which
of the following are famous figure skating pairs, and which are
methods for testing whether your data follow a... Continue Reading

If you perform linear regression analysis, you might need to
compare different regression lines to see if their constants and
slope coefficients are different. Imagine there is an established
relationship between X and Y. Now, suppose you want to determine
whether that relationship has changed. Perhaps there is a new
context, process, or some other qualitative change, and you want to
determine... Continue Reading

At the start of a new year, I like to look for data that’s
labeled 2016. While it’s not necessarily new for 2016, one of the
first data sets I found was healthcare.gov’s
data about qualified health and stand-alone dental plans
offered through their site.
Now, there’s lots of fun stuff to poke around in a data set this
size—there are over 90,000 records on more than 140 variables. But
to start out I... Continue Reading

In an earlier post, I shared an
overview of acceptance sampling, a method that lets you
evaluate a sample of items from a larger batch of products (for
instance, electronics components you've sourced from a new
supplier) and use that sample to decide whether or not you should
accept or reject the entire shipment.
There are two approaches to acceptance sampling. If you do it by
attributes, you... Continue Reading

Now that we've seen how easy it is to
create plans for acceptance sampling by variables, and to
compare different sampling plans, it's time to see how to
actually analyze the data you collect when you follow the sampling
plan.
If you'd like to follow along and you're not already using
Minitab, please download the free
30-day trial.
Collecting the Data for Acceptance Sampling by Variable
If you'll... Continue Reading

In my last post, I showed how to use Minitab Statistical
Software to
create an acceptance sampling plan by variables, using the
scenario of a an electronics company that receives monthly
shipments of LEDs that must have soldering leads that are at least
2 cm long. This time, we'll compare that plan with some other
possible options.
The variables sampling plan we came up with to verify the... Continue Reading

Earlier, I shared an
overview of acceptance sampling. Now we'll look at how to do
acceptance sampling by variables, facilitated by the tools in
Minitab Statistical Software. If you're not already using it
and you'd like to follow along, you can get the free
30-day trial version.
In contrast to acceptance
sampling by attributes, where inspectors make judgment calls about
defective items,... Continue Reading

If you're just getting started in the world of quality
improvement, or if you find yourself in a position where you
suddenly need to evaluate the quality of incoming or outgoing
products from your company, you may have encountered the term
"acceptance sampling." It's a statistical method for evaluating the
quality of a large batch of materials from a small sample of items,
which statistical
softwar... Continue Reading

In my last post, I walked
through the steps to
install Minitab 17 on a Mac using Apple Boot Camp.
Minitab 17 can also be installed on a Mac using desktop
virtualization software.
In addition to your Mac, you’ll need:
A copy of Windows 7 or later version ISO
Minitab 17 Statistical Software
Desktop virtualization software allows you to install and use
Windows on your Intel-based Mac without requiring... Continue Reading

While Minitab 17 is currently a
Windows-only application, there are people who only have a Mac
available for the installation who also find they need to use
Minitab 17.
It is possible to run Minitab 17 on a Macintosh, though the
steps involved in the installation can seem a little daunting at
first. In the Technical Support department, we sometimes hear
reluctance in people’s voices when we throw... Continue Reading