What do you mean by identfying subgroups within the membership base?
Let's say that until this week, every solicitation for donations you have ever sent out talked about a bright future for our children. This time you warned people that if our goals are not met, the bad guys will win. As it happens, both approaches did equally well.
What our system will notice is that the people responding to this latest solicitation are not the usual donors. In fact the group that has been consistently responding to the "bright future" solicitations did not donate much at all this time. Instead, a different group of people who had never donated before responded to this particular solicitation.
You are now a more effective fund-raiser. You have identified a second group of potential donors that you need to approach differently.