how many variables in a model should be useful how many variables in a model why don't you add variables to the equation which variables should be relevant in a model how many variables can you use in a data model how many variables should be included in a model of econometrics why don't you keep adding variable to model can variables be added to model but not all are related to the model? how many variables should be related to each response variable how many variables in the econometric model should be relevant to the response variable? how many variables are needed for a model how many parameters are in a model how to find the efficiency of a model how can you determine model efficiency which of the following variables should only be added to a model if it has reasons to believe it's relevant to the response variable? how many variables should be a response variable in model does each new variable have to be related to the answer? how many variables do you need in a model how many variables can you include in a model how much regressor is there in a model