SSA Results

For each important result, you need to know the mean and standard deviation (SD). If the standard deviation is small relative to the mean, you can be fairly confident of the result. See the RunGTAP/RunGEM SSA Help file for more details.

In the case of a dynamic simulation, you are told means and standard deviations in all periods.

Suppose that your scenario has Policy years 2010 to 2020. Then the SSA results calculated are packaged in 3 time series of reults for ViewSOL:

•a time series of means and SDs for the cumulative differences (between Policy and Rerun (or Base) from 2010 to 2020.

•a time series of means and SDs for the year-on-year Policy results from 2010 to 2020.

•a time series of means and SDs for the year-on-year Rerun (or Base if you are not doing the Rerun) results from 2010 to 2020.

You access these results in ViewSOL via the Sequence file for each of the 3 sets of results.

The cumulative difference Sequence file has a name like BBB-RRR-PPP-cd-SSSSS.SEQ where BBB,RRR and PPP are the 3-letter Sim Names for Base, Rerun and Policy and SSSSS is the 5-character SSA Name.

The Policy year-on-year Sequence file has the same name as the above except that "cd" is changed to "yy". The Rerun Sequence file has the same name as the year-on-year Policy Sequence file except that the PPP is omitted.

When you load the cumulative differences, you can check, for any period (eg for 2015 or 2017) what the mean is (the mean will be pretty close to the cumulative difference from the original simulation) and what the SD is. Then you can tell roughly how sensitive that cumulative difference result is (for the relevant period) to variations in the parameters you varied. Ditto for the year-on-year Policy or Rerun results at different periods.

Note that the Verbal Description on each SSA Solution file contains details of the SSA runs, including the SSA details (taken from the memo on the Sensitivity form). When you load one of the three time series of SSA results into ViewSOL, you can see these details by clicking on Description in the ViewSOL menus.

Sensitivity Report File

As for RunGEM and RunGTAP, a Sensitivity Report file (.SRP file) is produced giving some details of the SSA. Included are the SSA details (taken from the memo on the Sensitivity form). This Sensitivity Report file has the same short name as the cumulative difference Sequence file except that the "-cd" is omitted. That is, the name is of the form

BBB-RRR-PPP-SSSSS.SRP.

URL of this topic: www.copsmodels.com/webhelp/rundynam/hc_rundssaresults.htm

Link to full GEMPACK Manual

Link to GEMPACK homepage