Numbers generated by a mathematical formula which has the property that the generated numbers appear to be independent observations from a uniform distribution. Depending on the context, the distribution is usually a continuous uniform distribution on the interval (0, 1), or a discrete uniform distribution on the integers 0, 1,…, 9. Pseudo-random numbers are often referred to simply as random numbers (or random digits). They form the basis for many statistical methods including the bootstrap, Markov chain Monte Carlo methods and simulation. A short table of pseudo-random numbers is given in Appendix IX. It is conjectured that the decimal digits of π (3, 1, 4, 1, 5, 9,…) may be a naturally occurring sequence of random digits. See also ERNIE.