does taking the first difference of a series always give us a stationary series which test gives you a series that has a unit root and no series at all does taking the first difference of a series give us a stationary series? when a series has a unit root, does it always have a stationary series? how to tell if a random walk is stationary is there a stationary series how does taking first difference in a series always get us a stationary series does a series have a unit root do the first two difference units in a series always give you a stationary series when does the first difference between a series always give us a stationary series which unit root always gives us a stationary series? does taking first difference give us a stationary series? does taking the first difference of a series with a unit root always give us a stationary series? does a unit root in a series always indicate that it is a stationary series can a random walk have a unit root what is first difference in a series what do you use unit root for when determining the series does taking the first difference of a series with a unit root always give us a stationary series when i take the first difference does that change to a stationary series? when taking the first difference does random walk