Hi,
By definiation ex-post means "forecast for the past periods". The system checks about half of the history period and calculates forecast for this period based on the rest of the history.This helps the system to calculate the forecast accuracy. This way system checks the calculated forecast values (Ex-post forecast) against the actual sales history for the same periods.
Please also check SDN threads below:
Outlier:
An outlier is an historical value that lies outside the tolerance lane. The APO system calculates this tolerance lane on the basis of the sigma factor. It then corrects any historical value that lies outside the upper or lower band of this tolerance lance so that it corresponds to the calculated ex-post value for that point in time.
I hope this gives you some insight.
Regards
Datta