hello! thanks for the reply. right now, im currently pursuing two level full factorial with centerpoint. and yes, my variables are continuous.

however, im not really sure of the process. is the model im gonna come up is still linear? and then ill just be doing a follow up check whether there is curvature? im thinking this is the sequence:

1. evaluate the main effects

2. evaluate the itneraction effects

3. come up with model (equation) using multiple linear regression

4. test for curvature?

does this make sense? or in the equation im gonna come up, there is a term belonging to the curvature part? not really sure. if you have reference material or examples, that would really be a great help!