Quality Progress - March 2018 - 51

is important, but at least it won't
contaminate our interpretation
of the relationship between the
studied factors and our response.
Finally, statistical theory for the analysis depends on
randomization. The interpretation of p-values from an
analysis of variance or other analyses of the designed
experiment is tied to the assumption of the run order
and experimental units being randomly assigned.1
This theoretical underpinning means that we have
the ability to assess and quantify how likely the change
that we have observed for a particular factor or term in
our model can be attributed to chance. The smaller that
chance, the more confident that we feel about associating that observed change with the factor that we have
manipulated.
When thinking about randomization in the experiment, it also is important to make sure that we:

1. Design the experiment that we want with the factor
and factor levels that we want.
2. Fix whatever factors we are not manipulating.
3. Randomize over the run order of the experiment
and the assignment of experimental units to the
treatments. 2

Always random?

So, does that mean that we should always run a completely randomized experiment? No-there are other
types of designs to accommodate constraints and
situations during experimentation, while still preserving
the benefits of randomization. The following are three
different alternatives and the situations for which they
are suitable:
1. Blocking designs: These designs take into consideration that there are factors that cannot be randomly
assigned, or factors that cannot be controlled during the

FIGURE 4

18-run definitive screening design
X1

X2

X3

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Block

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1

a
Standard order

b
Note: Run in two blocks (of size 10 and 8, respectively), in which
after the first block has been run, there are data from all levels of all
factors and the main effects for all six factors can be estimated.

qualityprogress.com ❘ March 2018

QP 51


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Table of Contents for the Digital Edition of Quality Progress - March 2018

Seen and Heard
Expert Answers
Progress Report
Mr. Pareto Head
Career Coach
My Quality Story
In the Right Direction
A Different Kind of BBQ
Gaining Ground
Impeding Progress
Innovation Imperative
Statistics Spotlight
Standard Issues
Marketplace
Footnotes
Back to Basics
Quality Progress - March 2018 - INTRO
Quality Progress - March 2018 - cover1
Quality Progress - March 2018 - cover2
Quality Progress - March 2018 - 1
Quality Progress - March 2018 - 2
Quality Progress - March 2018 - 3
Quality Progress - March 2018 - 4
Quality Progress - March 2018 - 5
Quality Progress - March 2018 - Seen and Heard
Quality Progress - March 2018 - 7
Quality Progress - March 2018 - Expert Answers
Quality Progress - March 2018 - 9
Quality Progress - March 2018 - Progress Report
Quality Progress - March 2018 - 11
Quality Progress - March 2018 - 12
Quality Progress - March 2018 - Mr. Pareto Head
Quality Progress - March 2018 - Career Coach
Quality Progress - March 2018 - 15
Quality Progress - March 2018 - My Quality Story
Quality Progress - March 2018 - 17
Quality Progress - March 2018 - In the Right Direction
Quality Progress - March 2018 - 19
Quality Progress - March 2018 - 20
Quality Progress - March 2018 - 21
Quality Progress - March 2018 - 22
Quality Progress - March 2018 - 23
Quality Progress - March 2018 - A Different Kind of BBQ
Quality Progress - March 2018 - 25
Quality Progress - March 2018 - 26
Quality Progress - March 2018 - 27
Quality Progress - March 2018 - 28
Quality Progress - March 2018 - 29
Quality Progress - March 2018 - 30
Quality Progress - March 2018 - 31
Quality Progress - March 2018 - Gaining Ground
Quality Progress - March 2018 - 33
Quality Progress - March 2018 - 34
Quality Progress - March 2018 - 35
Quality Progress - March 2018 - 36
Quality Progress - March 2018 - Impeding Progress
Quality Progress - March 2018 - 38
Quality Progress - March 2018 - 39
Quality Progress - March 2018 - 40
Quality Progress - March 2018 - 41
Quality Progress - March 2018 - 42
Quality Progress - March 2018 - 43
Quality Progress - March 2018 - Innovation Imperative
Quality Progress - March 2018 - 45
Quality Progress - March 2018 - 46
Quality Progress - March 2018 - 47
Quality Progress - March 2018 - Statistics Spotlight
Quality Progress - March 2018 - 49
Quality Progress - March 2018 - 50
Quality Progress - March 2018 - 51
Quality Progress - March 2018 - 52
Quality Progress - March 2018 - 53
Quality Progress - March 2018 - Standard Issues
Quality Progress - March 2018 - 55
Quality Progress - March 2018 - 56
Quality Progress - March 2018 - 57
Quality Progress - March 2018 - Marketplace
Quality Progress - March 2018 - 59
Quality Progress - March 2018 - Footnotes
Quality Progress - March 2018 - 61
Quality Progress - March 2018 - 62
Quality Progress - March 2018 - 63
Quality Progress - March 2018 - Back to Basics
Quality Progress - March 2018 - cover3
Quality Progress - March 2018 - cover4
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