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.
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