What is the difference between a time series without autocorrelation, and a stationary time series?
If they are the same, why do we need to do both the Ljung-Box test and unit root test?
Consider a time series where the value at epoc is normally distributed with zero mean and variance and independedent of the values at all other epocs. The autocorrelation of this process is clearly zero for all non-zero lags and it is also clearly non-stationary.
Consider a time series where the value at epoc is normally distributed with zero mean and variance and independedent of the values at all other epocs. The autocorrelation of this process is clearly zero for all non-zero lags and it is also clearly non-stationary.
CB
One definition of a weakly stationary process is or with constant variance.
So, why do the above process with non-zero value of autocorrelation function for zero lags is stationary?