what is a discrete variable that can be used only once how are dummies used in regression modeling how many companies are able to run a dummy regression? why would a dummy be useful what is the difference between d0,d6 & d7 how to dummy a discrete variable what is the difference between d0, d6 and d7 what is the net frequency of a dummy for $p$ what is d6 in regression analysis what is true of the variable net$ which variable is used for the regression of the network frequency of d0, why is d7 a variable what is the dummy variable of p which dummies can be used in the regression of p$ what is net frequency of 0 what does net stand for? what dummies to use for ols does p$ equal to zero when there's more than one company on the market? what is d0 d6 when the value of net$ is zero