Hi all: I am planning to do the analysis using Response method. I have a Question regarding coding for my independednt variables. For example : X1 , X2, X3 are the independednt coded variables, however in my cases I also have combination tretament (eg. x1+x2). Usullay for the single independednt variables coding can be done as 1, 0, -1. I am very new to the programm so would like to get information on how the coding is done for combination treatment effect? Thank you so much and hope the way I am putting question make sense.
Example of the scinario:
Treatment 1: effect of Acid on bacterial growth
Treat 2: Effect of Protein on bacterial growth
Treat 3: Effect of Acid+protein on bacterial growth (How to do coding for combination/interaction effects )
It looks like they're all categorical variables, so you'll need to make indicator variables for these variables. Remember that if you have N levels you need n-1 indicators. Also, you interactions can then be specified as combinations of the other variables.
Learn how to run multiple linear regression models with and without interactions, presented by SAS user Alex Chaplin.
Find more tutorials on the SAS Users YouTube channel.