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Central Limit Theorems for Infinite Urn Models
An urn model is defined as follows: n balls are independently placed in an infinite set of urns and each ball has probability$p_k > 0$of being assigned to the kth urn. We assume that pk≥ pk + 1for all k and that ∑∞ k = 1pk= 1. A random variable Znis defined to be the number of occupied urns after...
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Published in: | The Annals of probability 1989-07, Vol.17 (3), p.1255-1263 |
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Main Author: | |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that cite this one |
Online Access: | Get full text |
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Summary: | An urn model is defined as follows: n balls are independently placed in an infinite set of urns and each ball has probability$p_k > 0$of being assigned to the kth urn. We assume that pk≥ pk + 1for all k and that ∑∞
k = 1pk= 1. A random variable Znis defined to be the number of occupied urns after n balls have been thrown. The main result is that Zn, when normalized, converges in distribution to the standard normal distribution. Convergence to N(0, 1) holds for all sequences {pk} such that$\lim_{n \rightarrow \infty} \operatorname{Var}Z_{N(n)} = \infty$, where N(n) is a Poisson random variable with mean n. This generalizes a result of Karlin. |
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ISSN: | 0091-1798 2168-894X |
DOI: | 10.1214/aop/1176991268 |