Terms in parameter estimates for two-way interactions of coded factors are being given as e.g. (EtOH + 0.1)*(n-PrOH-0.1)
I'm trying to work through an example out of Goos and Jones (Ch 3), where they've set up a DoE screen and model of select two-way ineractions. All factors except "Block" are continuous, and the factors are coded as -1 and +1 for the two levels tested. When fitting the model, I'm confused that the Parameter Estimates pulldown gives each interaction term not as e.g. EtOH*n-PrOH, but rather as (EtOH ...