| To ascertain nonstationarity or stationarity of time series variables, DF-GLS, Ng-Perron and KPSS tests are implemented. |
| Coefficients of the ARMA models are also checked for both stationarity and invertibility. |
| To test if a variable is stationary, a formal test of stationarity called the Augmented Dickey-Fuller test is commonly used. |
| Given the nature of time-series data, it is necessary to test the stationarity of each individual series. |
| The analysis begins by investigating the order of integration of the respective variables using a battery of unit root and stationarity tests. |
| A stationarity requirement, defined as a constant mean, variance and autocorrelation through time, constrains parameters to a certain range. |
