5.
Process Improvement
5.5.
Advanced topics
5.5.9.
An EDA approach to experimental design
5.5.9.10.
DOE contour plot
5.5.9.10.4.

How to Interpret: Best Corner


Four corners representing 2 levels for 2 factors

The contour plot will have four "corners" (two factors times two
settings per factor) for the two most important factors
X_{i} and X_{j}:
(X_{i}, X_{j}) = (, ), (, +), (+, ),
or (+, +). Which of these four corners yields the highest average
response ? That is,
what is the "best corner"?

Use the raw data

This is done by using the raw data, extracting out the two
"axes factors", computing the average response at each of the four
corners, then choosing the corner with the best average.
For the defective springs data, the raw data were
X_{1}

X_{2}

X_{3}

Y







67

+





79



+



61

+

+



75





+

59

+



+

90



+

+

52

+

+

+

87

The two plot axes are X_{1} and X_{3} and so the relevant raw data collapses to
X_{1}

X_{3}

Y





67

+



79





61

+



75



+

59

+

+

90



+

52

+

+

87


Averages

which yields averages
X_{1}

X_{3}

Y





(67 + 61)/2 = 64

+



(79 + 75)/2 = 77



+

(59 + 52)/2 = 55.5

+

+

(90 + 87)/2 = 88.5

These four average values for the corners are annotated
on the plot. The best (highest) of these
values is 88.5. This comes from the (+, +) upper right corner. We
conclude that for the defective springs data the best corner is (+, +).
