The battery of tests is named Diehard (see note 1). The algorithm that is implemented in Excel 2003 was developed by B.A. Wichman and I.D. Hill (see note 2 and note 3). This random number generator is also used in the RAT-STATS software package that is provided by the Office of the Inspector General, U.S. Department of Health and Human Services. It has been shown by Rotz et al (see note 4) to pass the DIEHARD tests and additional tests developed by the National Institute of Standards and Technology (NIST, formerly National Bureau of Standards).
- The tests were developed by Professor George Marsaglia, Department of Statistics, Florida State University and are available at the following Web site:
- Wichman, B.A. and I.D. Hill, Algorithm AS 183: An Efficient and Portable Pseudo-Random Number Generator, Applied Statistics, 31, 188-190, 1982.
- Wichman, B.A. and I.D. Hill, Building a Random-Number Generator, BYTE, pp. 127-128, March 1987.
- Rotz, W. and E. Falk, D. Wood, and J. Mulrow, A Comparison of Random Number Generators Used in Business, presented at Joint Statistical Meetings, Atlanta, GA, 2001.
C IX, IY, IZ SHOULD BE SET TO INTEGER VALUES BETWEEN 1 AND 30000 BEFORE FIRST ENTRY
IX = MOD(171 * IX, 30269)
IY = MOD(172 * IY, 30307)
IZ = MOD(170 * IZ, 30323)
RANDOM = AMOD(FLOAT(IX) / 30269.0 + FLOAT(IY) / 30307.0 + FLOAT(IZ) / 30323.0, 1.0)
Because RAND produces pseudo-random numbers, if a long sequence of them is produced, eventually the sequence will repeat itself. Combining random numbers as in the Wichman-Hill procedure guarantees that more than 10^13 numbers will be generated before the repetition begins. Several of the Diehard tests produced unsatisfactory results with earlier versions of RAND because the cycle before numbers started repeating was unacceptably short.