Return on Software: Maximizing the Return on Your Software Investment

Probability Functions

A probability function is a mathematical function that describes, for each outcome being considered, the probability of that outcome. A probability function is sometimes called a random variable. Figure E.2 shows the graph of the probability function for rolling a fair die.

Figure E.2. The probability function for a fair die

As a probability function, Figure E.2 is an example of a uniform distribution; each outcome has the same probability as the others. A uniform distribution represents our notion of fairness—each outcome is equally likely. When a distribution is not uniform, by definition some outcomes are more likely than ...