Questions

1. In our forecast, we modeled the increasing part of the time series using the trend function generated by Excel. We could also have used the moving average values. How can that be done? Try it and compare the results.
2. Change the values of the seasonality and confidence interval and study how the forecast diagram and parameters change.
3. How can you calculate the covariance between two values in a time series?
4. A possible way to make the variance independent of time is to take the logarithm of the time series values. Try this in the air passengers series and check the values of the variance.