what is unit root in time series which time series test for unit root when time series is tested for unit root by why is unit root test not found which test is preferred? what is unit root time series test for unit root which unit root time series is tested by adf, pp, kpss, which time series is tested for unit root by adf, ppp, kpss,... which is preferred for a time series which time series is tested for unit root by adf, pp, kpss, us why are unit roots found in time series if time series is tested for unit root by adf, pp, kpss, kpss, kpss,... which one is preferred? which test is preferred which time series is tested for unit root? time series testing for unit root what time series are tested for unit root what is unit root testing which time series is tested for unit root which time series would you test for unit root