1. A computerized method performed on a computer, the method comprising: providing output on a screen of the computer from a cause-and-effect model, to a user, wherein the providing includes displaying output effect values; receiving in the computer from the user one or more desired effect values that are different from one or more corresponding of the output effect values; and modifying, in the computer, the cause-and-effect model as a function of difference between the one or more desired effect values and the one or more corresponding output effect values.