which is the difference in difference of controlling and control variables difference in difference definition difference between dependent and control variable can a variable have a difference what is the difference in the difference between control variables and dependent variable which control variable is used as the policy control variable? control variables difference what variables to add for difference? differences in difference estimation difference in difference estimation difference of difference in effect difference between dependent and control variables difference in difference analysis which type of variable is an example of control variable? difference in difference calculation definition difference in difference between dependent and control variable difference between dependent and control variables which of the following variables would affect policy affect on the dependent variable what type of variable does policy affect in the difference? why is control and control variables added