What are the coordinates of the following points in a CCD?
a. central point (Blue round sign)
b. the N axis point (Red round sign)
c. 2N-f factorial points located at the corners (Yellow round sign)
Does it change with the type of Distribution Function used (Gaussian or
The PDDOEL documentation indicates the points are based on probability
so the location would be based on the design variable distribution.
If the variable has a gaussian distribution (PDVAR,,GAUS) then the probabilities
will be based on a Gaussian distribution. If the variable is uniform (PDVAR,,UNIF)
then the probabilities will be based on a uniform distribution. This can be verified
by looking at the sample points used in the database (file.pds) or in the sample file (file.samp).
For example, if a random variable has a gaussian distribution with mean of 10 and
standard deviation of 1, the sample values will be at the following locations.
Probability Level = .005 ( - 2.58 sigma ) => 7.42
Probability Level = .05 ( - 1.65 sigma) => 8.35
Probability Level = .50 ( 0 sigma) => 10.00
Probability Level = .95 ( +1.65 sigma) = 11.65
Probability Level = .995 ( +2.58 sigma) = 12.58