In statistics, a probability plot is a graphical technique for comparing two data sets, either two sets of empirical observations, one empirical set against a theoretical set, or (more rarely) two theoretical sets against each other. It commonly means one of:
- P–P Plot, "Probability-Probability" or "Percent-Percent" plot;
- Q–Q Plot, "Quantile-Quantile" plot, which is more commonly used. Special cases include the
Normal probability plot, a Q–Q plot against the standard normal distribution; The term "probability plot" may be used to refer to both of these types of plot, or the term "probability plot" may be used to refer specifically to a P-P plot.