The Common Discrete Probability Functions
This is a companion Web site to
P-values for the Popular Distributions
Discrete Random Variables: A discrete random variable is used to model a random outcome with a finite or countable number of possible outcomes. That is, a discrete random variable is one that may take on only a countable number of distinct values. If a random variable can take only a finite number of distinct values, then it must be discrete. Examples are the number of patients in a doctor's surgery, the number of defective light bulbs in a box of ten.
Probability Mass Function: The probability mass function of a discrete random variable is a list of probabilities associated with each of its possible values. It is also sometimes called the probability function or the probability mass function, i.e., p = P (X = x).
Cumulative Distribution Function: The cumulative distribution function of a random variable is a function giving the probability that the random variable X is less than or equal to x, for every value x, i.e. F = P(X £ x)
Statistical Thinking for Decision Making
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