Selecting a field in the Training Data as a Detail Key is optional, but strongly recommended. It represents the finest of level of detail at which calculations are of interest, like a policy number for example. Using a Detail Key will ensure that final model calculations will be performed at this level of detail. Otherwise these calculations will only be performed at the level described by unique combinations of characteristic bins within the input data.
If no Detail Key is selected, MultiRate will ask if one should be created after fields have been identified in the Column Selection window:
If the response is yes, a field named "detailKey" will be added to the Training Data table with unique values 1 through the # of records in the table and then automatically selected as the Detail Key. Otherwise the column selections will remain as is, with no Detail Key.
Also, selecting a Detail Key allows the Curve Modification calculation to be performed.
With regard to analyzing competing model structures, running each with a common Detail Key for each model is necessary for comparing fit statistics.