The Exposure field is the variable expected to have the strongest relationship with the Target variable. If no field is selected to be the exposure field, each record in the input table will be treated as an exposure of 1 by default.
If an exposure field is selected, it cannot contain NULL values. If the Training Data does happen to contain NULL values in the column meant to be used as the exposure, a Filter can be used to exclude records where the exposure column is NULL.
The model construct is:
so it is ideal for the relationship between the Exposure field and the Target variable to be linear.
The Exposure field may also be used as a Characteristic in the analysis. The system will ask whether to include the Exposure field as a Characteristic when the Column Selection window is closed. This option would be appropriate any time the relationship between Exposure and Target may not be perfectly linear.