The data for a binomial test is assumed to come from n independent trials, and have outcomes in either of two classes. The other assumption is that the probability of each outcome of each trial is the same, designated p. The values of the outcome could come directly from the data, where the value is always one of two kinds. More commonly, however, the test is applied to the sign of the difference between two values. If the probability is 0.5, this is the oldest of all nonparametric tests, and is called the ‘sign test’. Where the sign of the difference between two values is used, the binomial test reports whether the probability that the sign is positive is a particular p_value, p*.