Users often contact Minitab technical support to ask how the
software calculates the control limits on control charts.
A frequently asked question is how the control limits are
calculated on an
I-MR Chart or Individuals Chart. If Minitab plots the upper and
lower control limits (UCL and LCL) three standard deviations above
and below the mean, why are the limits plotted at values other than
3 times... Continue Reading

As a person who loves baking (and eating) cakes, I find it
bothersome to go through all the effort of baking a cake when the
end result is too dry for my taste. For that reason, I decided to
use a designed experiment in Minitab to help me reduce the moisture
loss in baked chocolate cakes, and find the optimal settings of my
input factors to produce a moist baked chocolate cake. I’ll share
the... Continue Reading

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While there are many graph options available in
Minitab’s Graph menu, there is no direct option to
generate a waterfall chart. This type of graph helps visualize the
cumulative effect of sequentially introducing positive or negative
values.
In this post, I’ll show you the steps to follow to make Minitab
display a waterfall chart even without a "waterfall chart" tool. If
you don’t already have... Continue Reading

Since the release of Minitab
Express in 2014, we’ve often received questions in technical
support about the differences between Express and Minitab 17.
In this post, I’ll attempt to provide a comparison between these
two Minitab products.
What Is Minitab 17?
Minitab 17 is an all-in-one graphical and statistical analysis
package that includes basic analysis tools such as hypothesis
testing,... 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

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

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

While many Six Sigma practitioners and other quality improvement
professionals like to use the Fishbone
diagram in Companion for brainstorming because of its ease of
use and integration with other Companion by
Minitab tools, some Minitab users find an infrequent need
for a Fishbone diagram. For the more casual user of the Fishbone
diagram, Minitab has the right tool to get the job done.
Minitab’s... Continue Reading

We often receive questions about moving ranges because they're
used in various tools in our statistical software,
including control charts and capability analysis when data is not
collected in subgroups. In this post, I'll explain what a moving
range is, and how a moving range and average moving range are
calculated.
A moving range measures how variation changes over time when
data are collected as... Continue Reading

Since opening a new
office in Phoenix to support our customers on the West Coast,
some evenings in Minitab technical support feel busier than others.
(By evenings, I mean after 5:30 p.m. Eastern time, when the members
of our tech support team in Pennsylvania go home for the day, and I
become an office of one.)
The variability in terms of days
that felt extremely busy versus days that didn’t... 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

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

When data are collected in subgroups, it’s easy to understand
how the variation can be calculated within each of the subgroups
based the subgroup range or the subgroup standard deviation.
When data is not collected in subgroups (so the subgroup size is
1), it may be a little less intuitive to understand how
within-subgroup standard deviation is calculated. How does
Minitab Statistical Softwarecalcu... Continue Reading

The two previous posts in this series focused on manipulating
data using Minitab’s
calculator and the
Data menu.
In
this third and final post, we continue to explore helpful features
for working with text data and will focus on some features in
Minitab’s Editor menu.
Using the Editor Menu
The Editor menu is unique in that the options displayed depend
on what is currently active (worksheet, graph,... Continue Reading

My previous post focused on
manipulating text data using Minitab’s calculator.
In this post we continue to explore some of the useful tools for
working with text data, and here we’ll focus on Minitab’s Data
menu. This is the second in a 3-part series, and in the final post
we’ll look at the new features in Minitab’s Editor menu.
Using the Data Menu
When I think of the Data menu, I think... Continue Reading

With Minitab, it’s easy to create graphs and manage numeric,
date/time and text data. But Minitab’s enhanced data manipulation
features make it easier to work with text data, too.
This
is the first of three posts in which I'm going to focus on various
tools in Minitab that are useful when working with text data,
including the Calculator, the Data menu, and the Editor menu.
Using the Calculator
You... Continue Reading

In technical support, we often receive questions about
Gage R&R and how Minitab calculates the amount of
variation that is attributable to the various sources in a
measurement system.
This post will focus on how the variance components are
calculated for a crossed Gage R&R using the ANOVA table, and
how we can obtain the %Contribution, StdDev, Study Var and %Study
Var shown in the Gage R&R output. ... Continue Reading

Minitab's capability analysis output gives you estimates of the
capability indices Ppk and Cpk, and we receive many questions about
the difference between them. Some of my colleagues have taken other
approaches to explain the difference between Ppk and Cpk, so I
wanted to show you how they differ by detailing precisely how each
one is calculated.
When you're using statistical softwarelike Minitab,... Continue Reading

In technical support, we frequently receive calls from Minitab
users who have questions about the differences between Cpk and
Ppk.
Michelle Paret already wrote a great post about the
differences between Cpk and Ppk, but it also helps to have a
better understanding of the math behind these numbers. So in this
post I will show you how to calculate Ppk using Minitab’s default
settings when the... Continue Reading