DPL offers a means for combining the probability assessments of multiple experts into a single likelihood (probability of occurrence). To do this, each expert must provide an assessed probability distribution, and a weight must be assigned to each expert. DPL offers an input interface for the process of determining these weights and calculating the expected likelihood. The weights used by DPL are determined by the "reliability" of the expert and the amount of shared information (overlap) among the experts.
Note that an expert's reliability is determined by the range of his or her assessments; it is assumed that more "reliable" experts provide tighter distributions around their assessments. Caution should be used to make sure experts are properly calibrated and that their assessments accurately reflect their knowledge and experience.
You may only enter multiple expert data for unconditioned two-state discrete chance nodes.
Entering Assessments of Multiple Experts
- Double-click the discrete chance node for which you wish to enter the assessments of multiple experts.
- Ensure the node is unconditioned and is a two-state node.
- Select the Data tab if it is not already selected.
- Click the Multiple Experts... button. DPL displays the Combine Expert Opinions dialog.
- Begin entering data with the most reliable expert (the most reliable expert is the one with the narrowest band between his/her 10th and 90th percentiles).
- Under the Expert heading in the Name entry box, type the name of the expert.
- In the Fractiles section, type the 10th, 50th, and 90th percentiles of the expert's assessed probability distribution.
- In the Overlap entry box, type the overlap factor of the expert (the most reliable/first expert has an overlap factor of 0).
- Click Add.
- Repeat steps the preceding four steps for each remaining expert in the order of descending reliability.
Experience Indices
The reliability of each expert is ranked by the experience score. The experts must be listed in order of greatest to least experience. If this is not the case, DPL will display a warning and ask you to re-rank the experts. To change the rank of an expert, click on the number of the expert. In the "Expert" section, change the expert's rank, then click Update. DPL re-ranks the experts using the new ranking. If further experts are ranked incorrectly, repeat the process until all experts are correctly ranked.
Editing/Clearing Multiple Experts Data
Once you have entered multiple expert data using the Combine Expert Opinions dialog, DPL displays it as "Multiple Experts: p". Also, you will not be able to enter probability data directly on the Data tab of the Node Definition dialog. You need to click Multiple Experts to edit it again.
To clear the multiple experts data, click select each of the Multiple Experts listed and press the delete button to delete all the data for all experts. Click OK to close the dialog. You will now be able to edit the probability data directly on the Data tab of the Node Definition dialog.
Versions: DPL Enterprise, DPL PortfolioSee Also