I am confused about the output of a unit root test I performed. After taking data with a seasonal effect in seasonal differences, the time-plot and the correlogram (shown below) both suggest non-stationarity.
But when performing the unit root test, the null hypothesis of non-stationarity is rejected.
So now I don't know what to assume; stationarity or not? When I take the data in first differences, the same problem stays.
Can you guys maybe help?