A binomial experiment is defined as an experiment that is repeated a fixed number of times, n, with only two possible outcomes - success or failure. The probability of success, p, is constant across all trials. Common notation includes n for the number of trials, p for the probability of success, q for the probability of failure (where q = 1 - p), and x for the number of successful trials out of n. An example is rolling a pair of dice 5 times to see how many doubles (pairs where both dice show the same number) occur.