| Experimental design involves
conducting a systematic series of tests
to discover the relationship between the
factors that affect a process and the response.
The factors are varied in a systematic fashion
and the resulting response observed. The
results of the experiment are analyzed to
find the regression equation that relates
the factors to the response.
The Design of Experiments (Experimental
Design) is used when a process is affected
by several different factors. In an experimental
design several factors are varied at the
same time. This gives more information for
less testing than the 'One Factor at a Time'
(OFAT) method in which each factor is varied
in turn whilst the others remain constant.
It also allows 'interactions'
between factors to be evaluated, and the
effects of interactions are usually important.
The two main approaches to experimental
design are the 'classical' and 'Taguchi'
methods'. Experts are divided
on the merits of the Taguchi method, but
the emphasis on variation and the methods
it uses to address variation are important.
The types of design commonly used included
Factorial
Designs and Fractional
Factorial Designs and Plackett-Burman
Designs.
A more powerful approach is to use Response
Surface Methods; this group
includes the Box
Behnken and Central
Composite Designs (CCD).
Designs that involve mixtures require a
different method of analysis, see the topic
on Mixture
Designs.
Terms used in the Design of Experiments
include:
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