ProbabilityAxioms

(These axioms are just the most elementary way to define probabilities. Other axiom schema are used with non-discrete points.)

Let U be a SeT of discrete points, e1,e2,e3..., called elementary events. We call this set, the universe or sample space.

Let every elementary event, e in U, have a non-negative weight, w(e), assigned to it.

Let composite events, Y1,Y2,Y3,... be represented by SubSets of U.

Define the probability of an event X (any subset of U), as the sum of the weights, w(e), for every elementary event contained in X divided by the sum of the weights of every element of U.

DickBeldin