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; wherein the cause-and-effect model includes a matrix of causes and effects, with numerical values each representing an influence the corresponding cause has on the corresponding effect; and wherein the modifying includes changing numerical influence values as a function of the difference between the one or more desired effect values and the one or more corresponding output effect values; and further comprising, prior to the providing the output, constructing the cause-and effect model, wherein the constructing includes: receiving from the user the matrix of causes and effects, wherein the matrix of causes and effects is entered into the computer using a graphical user interface of the computer; and receiving from the user the numerical influence values for the matrix.