9. The method of claim 8 , wherein the second ML model specifies: (i) a weighted coefficient value for processing items of supporting evidence for the first candidate answer, and (ii) a plurality of supporting evidence feature score values, wherein each supporting evidence feature score value of the plurality of supporting evidence feature score values was observed during a training session of the QA system using supporting evidence processing for each of a plurality of candidate answers generated during the training session.
10. The method of claim 9 , wherein the measure of expected change is generated by computing a product of the weighted coefficient value and a first one of: (i) an average of the plurality of supporting evidence feature score values in the second ML model, (ii) a maximum value of the plurality of supporting evidence feature score values, and (iii) a selected one of the plurality of supporting evidence feature score values that is greater than a threshold percentage of the plurality of supporting evidence feature score values, wherein the measure of expected change to the first confidence score value is determined by computing a product of the weighted coefficient value and a second one of: (i) the average of the plurality of supporting evidence feature score values in the second ML model, (ii) the maximum value of the plurality of supporting evidence feature score values, and (iii) the selected one of the plurality of supporting evidence feature score values that is greater than the threshold percentage of the plurality of supporting evidence feature score values.