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5.
Process Improvement
5.1.
Introduction
5.1.2.
What are the uses of DOE.
DOE is a
multipurpose
tool that can
help in many
situations
Below are seven examples illustrating situations in which experimental design can be used
effectively:
Choosing Between Alternatives
q
Selecting the Key Factors Affecting a Response
q
Response Surface Modeling to:
Hit a Target
r
Reduce Variability
r
Maximize or Minimize a Response
r
Make a Process Robust (i.e., the process gets the "right" results even though there
are uncontrollable "noise" factors)
r
Seek Multiple Goals
r
q
Regression Modeling
q
Choosing Between Alternatives (
Comparative Experiment
)
A common
use is
planning an
experiment
to gather
data to make
a decision
between two
or more
alternatives
Supplier A vs. supplier B. Which new additive is the most effective. Is catalyst `x' an
improvement over the existing catalyst. These and countless other choices between alternatives
can be presented to us in a never-ending parade. Often we have the choice made for us by outside
factors over which we have no control. But in many cases we are also asked to make the choice.
It helps if one has valid data to back up one's decision.
The preferred solution is to agree on a measurement by which competing choices can be
compared, generate a sample of data from each alternative, and compare average results. The
'best' average outcome will be our preference. We have performed a
comparative experiment
!
Types of
comparitive
studies
Sometimes this comparison is performed under one common set of conditions. This is a
comparative study with a narrow scope - which is suitable for some initial comparisons of
possible alternatives. Other comparison studies, intended to validate that one alternative is
perferred over a wide range of conditions, will purposely and systematically vary the background
conditions under which the primary comparison is made in order to reach a conclusion that will
be proven valid over a broad scope. We discuss experimental designs for each of these types of
comparisons in Sections
5.3.3.1
and
5.3.3.2.
Selecting the Key Factors Affecting a Response (
Screening Experiments
)
5.1.2. What are the uses of DOE.
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