Natalie, I believe the 'all possible models' option in the stepwise platform simply considers all combinations of factors up to a set number of factors being in the model. That is, if you have 3 x's, call them A, B and C then JMP would fit all the following models: A B C A+B A+C B+C A+B+C For each of the models it would calculate fit and then list them so you could identify the best. So, instead of using a logic based stepwise system, it's a 'brute force' type of model fitting.
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