when is it appropriate to use a time-dummy in mri when should time dummies be used when do you use time dummies? when should i use time dummies when to use time dummies when to use time dummies do time dummy models work in multiple regression when to use time dummies in regression when to use dummies in multiple regression when to include time dummies in regression when to use time dummies in regression analysis when should time dummies be used when should one use time dummies in multiple regression when are time dummies used when to use dummies in regression analysis why to use time dummies in regression when do time dummies in the multiple regression analysis work? why not why use time dummies in multiple regression when should time dabble be used in regression why do you need time dummies