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A response surface design that has points
at:
- the center
- the midpoint of each side
There are no corner points. The design
is spherical, all the points (except the
center point) lie on a sphere of radius
See Central Composite Design
A response surface design that has points
at:
- the center
- the corner points
- axial points at 'a'
from the center
The design is usually rotatable, if the
correct value of a
is selected
A technique used in the Design of Experiments
to find the maximum or minimum, if it is
not contained within the initial parameter
settings. It involves:
- carrying out an initial experiment and,
if it does not contain the [maximum/minimum],
- finding the path of steepest [ascent/descent]
- carrying out a test at intervals point
along the path until it starts to [ascend/descend]
- carry out an experiment around the highest
point on the path to see if it is the
[maximum/minimum]
- if not find the path of steepest ascent,
and continue the search
The experiments may be first order designs
with center points. If the curvature is
non-significant the experimental region
does not contain the center point and the
path of steepest ascent can be found. If
the curvature is large the additional testing
required for a second order design is carried
out.
Response surface design is a types of Experimental
Design that investigate curvature of the
response surface. They achieve this by using
a quadratic regression equation rather than
the linear form of the regression equation
used in factorial designs.
When the true response surface is approximated
by a linear equation the maximum and minimum
values at a corner point. Response surface
designs can have the maximum or minimum
in the interior of the surface. This allows
the response to be optimized using hill
climbing methods.
There are various types of response surface
design including the Central Composite (CCD)
and Box Behnken designs.
See Hill Climbing
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