释义 |
RunA run is a sequence of more than one consecutive identical outcomes, also known as a Clump. Given Bernoulli Trials (say, in theform of Coin Tossings), the probability of a run of consecutive heads or tails is given by the Recurrence Relation
| (1) |
where for and (Bloom 1996).
Let denote the number of sequences of indistinguishable objects of type and indistinguishableobjects of type in which no -run occurs. The probability that a -run does occur is then givenby
| (2) |
where is a Binomial Coefficient. Bloom (1996) gives the following recurrence sequence for,
| (3) |
where
| (4) |
Another recurrence which has only a fixed number of terms is given by | | | (5) | where
| (6) |
(Goulden and Jackson 1983, Bloom 1996). These formulas disprove the assertion of Gardner (1982) that``there will almost always be a clump of six or seven Cards of the same color'' in a normal deck of cards by giving.
Given Bernoulli Trials with a probability of success (heads) , the expected number of tails is , so the expected number of tail runs is . Continuing,
| (7) |
is the expected number of runs . The longest expected run is therefore given by
| (8) |
(Gordon et al. 1986, Schilling 1990). Given 0s and 1s, the number of possible arrangements with runs is
| (9) |
for an Integer, where is a Binomial Coefficient. Then
| (10) |
Bloom (1996) gives the expected number of noncontiguous -runs in a sequence of 0sand 1s as
| (11) |
where is the Pochhammer Symbol. For , has an approximately Normal Distribution withMean and Variance
See also Coin Tossing, Eulerian Number, Permutation, s-Run References
Bloom, D. M. ``Probabilities of Clumps in a Binary Sequence (and How to Evaluate Them Without Knowing a Lot).'' Math. Mag. 69, 366-372, 1996.Gardner, M. Aha! Gotcha: Paradoxes to Puzzle and Delight. New York: W. H. Freeman, p. 124, 1982. Godbole, A. P. ``On Hypergeometric and Related Distributions of Order .'' Commun. Stat.: Th. and Meth. 19, 1291-1301, 1990. Godbole, A. P. and Papastavnidis, G. (Eds.). Runs and Patterns in Probability: Selected Papers. New York: Kluwer, 1994. Gordon, L.; Schilling, M. F.; and Waterman, M. S. ``An Extreme Value Theory for Long Head Runs.'' Prob. Th. and Related Fields 72, 279-287, 1986. Goulden, I. P. and Jackson, D. M. Combinatorial Enumeration. New York: Wiley, 1983. Mood, A. M. ``The Distribution Theory of Runs.'' Ann. Math. Statistics 11, 367-392, 1940. Philippou, A. N. and Makri, F. S. ``Successes, Runs, and Longest Runs.'' Stat. Prob. Let. 4, 211-215, 1986. Schilling, M. F. ``The Longest Run of Heads.'' Coll. Math. J. 21, 196-207, 1990. Schuster, E. F. In Runs and Patterns in Probability: Selected Papers (Ed. A. P. Godbole and S. Papastavridis). Boston, MA: Kluwer, pp. 91-111, 1994. |