The Theory
Response Suface Analysis (RSA) is a method from the wider field of Response Surface Methodologies (RSM).
Requirements
Commensurable Scales
Commensurability explained as briefly as possible is that two scales are measured in the same
units. In the world of Likert-scales this mostly means they are measured on the same number of
points.
Centered on a Common Point
There is a number of ways this can be done.