For a Process output, y, which is a function of several Factors (x's), that is, for
the Design of Experiments (DOE) discipline can design the most efficient and
effective experiments to determine the values of the x's which produce the optimal value for -- or the minimal Variation in -- the Response Variable, y.
DOE is active and controlling. (This can be done with Processes, but usually not with Populations). DOE doesn’t collect or measure existing data with pre-existing values for y and the x’s. DOE specifies Combinations of values for inputs (Factors) and then measures the resulting values of the outputs (Responses). This is the Design of the Experiment.
Statistical software packages perform DOE calculations which specify the elements which make up the Design:
Andrew A. (Andy) Jawlik is the author of the book, Statistics from A to Z -- Confusing Concepts Clarified, published by Wiley.