Blog posts and articles about testing hypotheses with the statistical method called the T-Test.

Along with the explosion of interest in visualizing data over
the past few years has been an excessive focus on how attractive
the graph is at the expense of how useful it is. Don't get me
wrong...I believe that a colorful, modern graph comes across better
than a black-and-white, pixelated one. Unfortunately, however, all
the talk seems to be about the attractiveness and not the value of
the... Continue Reading

T-tests are handy hypothesis tests in statistics when you want to
compare means. You can compare a sample mean to a hypothesized or
target value using a one-sample t-test. You can compare the means
of two groups with a two-sample t-test. If you have two groups with
paired observations (e.g., before and after measurements), use the
paired t-test.
How do t-tests work? How do t-values fit in? In this... Continue Reading

People say that I overthink everything. I've given this
assertion considerable thought, and I don't believe that it is
true. After all, how can any one person possibly overthink every
possible thing in just one lifetime?
For example, suppose I live 85 years. That's 2,680,560,000
seconds (85 years x 365 days per year x 24 hours per day x 60 min
per hour x 60 seconds per minute). I'm asleep about a... Continue Reading

About
a year ago, a reader asked if I could try to explain
degrees of freedom in statistics. Since then,
I’ve been circling around that request very cautiously, like it’s
some kind of wild beast that I’m not sure I can safely wrestle to
the ground.
Degrees of freedom aren’t easy to explain. They come up in many
different contexts in statistics—some advanced and complicated. In
mathematics, they're... Continue Reading

I used to work
in the manufacturing industry. Some processes were so complex that
even a very experienced and competent engineer would not
necessarily know how to identify the best settings for the
manufacturing equipment.
You could make a guess using a general idea of what should be
done regarding the optimal settings, but that was not sufficient.
You need very precise indications of the correct... Continue Reading

I am a bit of an Oscar fanatic.
Every year after the ceremony, I religiously go online to find out
who won the awards and listen to their acceptance speeches. This
year, I was so chuffed to learn that Leonardo Di Caprio
won his first Oscar for his performance in The Revenant in
the 88thAcademy
Awards—after five nominations in previous ceremonies. As a
longtime Di Caprio fan, I still remember... Continue Reading

For the majority of my career with
Minitab, I've had the opportunity to speak at conferences and other
events somewhat regularly. I thought some of my talks were pretty
good, and some were not so good (based on ratings, my audiences
didn't always agree with either—but that's a topic for another
post). But I would guess that well over 90% of the time, my
proposals were accepted to be presented at... Continue Reading

While
the roots of Lean Six Sigma and other quality improvement
methodologies are in manufacturing, it’s interesting to see how
other organizational functions and industries apply LSS tools
successfully. Quality improvement certainly has moved far beyond
the walls of manufacturing plants!
For example, I recently had the opportunity to talk to Drew
Mohler, a Lean Six Sigma black belt and senior... 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

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

P-values are frequently misinterpreted, which causes many
problems. I won't rehash those
problems here here since my colleague Jim Frost has
detailed the issues involved at some length, but the fact remains
that the p-value will continue to be one of the most frequently
used tools for deciding if a result is statistically
significant.
You know the old saw about "Lies, damned lies, and... Continue Reading

This
past weekend in the Big Ten showed how being conservative on 4th
down decisions can cost you a game. Ohio State punted on 4th and 1
three different times, while Penn State and Illinois both kicked
field goals in the 4th quarter when they needed a touchdown to tie
or take the lead. All three teams lost. Perhaps taking some advice
from the 4th down calculator would have greatly benefited them!
If... Continue Reading

Back when I was an undergrad in
statistics, I unfortunately spent an entire semester of my life
taking a class, diligently crunching numbers with my TI-82, before
realizing 1) that I was actually in an Analysis of Variance (ANOVA)
class, 2) why I would want to use such a tool in the first place,
and 3) that ANOVA doesn’t necessarily tell you a thing about
variances.
Fortunately, I've had a lot more... Continue Reading

Control charts are a fantastic tool. These charts plot your
process data to identify common cause and special cause variation.
By identifying the different causes of variation, you can take
action on your process without over-controlling it.
Assessing the stability of a process can help you determine
whether there is a problem and identify the source of the problem.
Is the mean too high, too low,... Continue Reading

By Matthew Barsalou, guest
blogger
A problem must be understood before it can be properly
addressed. A thorough understanding of the problem is critical when
performing a
root cause analysis (RCA) and an RCA is necessary if an
organization wants to implement corrective actions that truly
address the root cause of the problem. An RCA may also be necessary
for process improvement projects; it is... Continue Reading

Since it's the Halloween season, I want to share how a classic
horror film helped me get a handle on an extremely useful
statistical distribution.
The
film is based on John W. Campbell's classic novella "Who Goes
There?", but I first became familiar with it from John
Carpenter's 1982 film The Thing.
In the film, researchers in the Antarctic encounter a predatory
alien with a truly frightening... Continue Reading

In Part 5 of our series, we began the analysis of
the experiment data by reviewing analysis of covariance and
blocking variables, two key concepts in the design and
interpretation of your results.
The
250-yard marker at the Tussey Mountain Driving Range, one of the
locations where we conducted our golf experiment. Some of the
golfers drove their balls well beyond this 250-yard maker during a
few of... Continue Reading

In
Part 3 of our series, we decided to test our 4
experimental factors, Club Face Tilt, Ball Characteristics, Club
Shaft Flexibility, and Tee Height in a full factorial design
because of the many advantages of that data collection plan.
In Part 4 we concluded that each golfer
should replicate their half fraction of the full factorial 5 times
in order to have a high enough power to detect... Continue Reading

Every
single Big Ten team played a conference game this week, giving us
the most 4th downs to analyze yet. Last week, 4 of the 6 games were decided by one
possession. This week only 2 of the 7 games were decided by one
possession, so let's see if the losing teams missed opportunities
to keep the game close! But first, a quick refresher on what this
is.
I've used Minitab Statistical Software to... Continue Reading