Combining CFs

The CF for hypothesis h in a rule is a product of CFs for the evidence and rule divided by 100. Now, suppose we have two rules for the same hypothesis h, with the confidence factors CF1 = 70 and CF2 = 30, respectively. We also assume that the information sources for the evidence in these rules are independent. Then the combined confidence factor (CFcomb) is calculated as follows:

CFcomb = CF1 + CF2 – (CF1*CF2)/100 = 79.

When another rule becomes available that is related to the same hypothesis, with, say, CF3  = 30, the CF for the hypothesis is recalculated:

CFcombnew = CF3 + CFcomb – (CF3 * CFcomb)/100 = 85.

This is continued until all the evidence for h is combined.