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Theory of Statistics - George Mason University

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Notes and Further Reading 143<br />

After existence <strong>of</strong> a solution, the next question is whether the solution is<br />

unique, or in our formulation <strong>of</strong> the problem, whether the moments uniquely<br />

determine the probability distribution.<br />

Many <strong>of</strong> the results concerning the moment problem involve probability<br />

distributions that are not widely used. Heyde (1963) was the first to show<br />

that a particular interesting distribution, namely the lognormal distribution,<br />

was not uniquely determined by its moments. (This is Exercise 1.28.)<br />

Corollary 1.18.1 is due to Thomas Stieltjes who proved it without use <strong>of</strong><br />

Theorem 1.18. Pro<strong>of</strong>s and further discussion <strong>of</strong> the theorem and corollary can<br />

be found in Shohat and Tamarkin (1943).<br />

Sequences and Limit Theorems<br />

The various forms <strong>of</strong> the central limit theorem have a long history <strong>of</strong> both<br />

both the theory and the applications. Petrov (1995) provides an extensive<br />

coverage. Dudley (1999) discusses many <strong>of</strong> the intricacies <strong>of</strong> the theorems and<br />

gives extensions <strong>of</strong> the theory.<br />

The most important seminal result on the limiting distributions <strong>of</strong> extreme<br />

values was obtained by Fisher and Tippett (1928). von Mises (de Misès) (1939)<br />

and Gnedenko (1943) cleaned up some <strong>of</strong> the details, and Theorem 1.59 is essentially<br />

in the form stated in Gnedenko (1943). The limiting distributions <strong>of</strong><br />

extreme values are discussed at some length by David and Nagaraja (2003),<br />

de Haan and Ferreira (2006), and Galambos (1978); and as mentioned in the<br />

text, a pro<strong>of</strong> <strong>of</strong> Theorem 1.59, though not the same as given by Gnedenko is<br />

given by de Haan and Ferreira.<br />

De Finetti’s theorem allows the extension <strong>of</strong> certain results for independent<br />

sequences to similar results for exchangeable sequences. Taylor et al. (1985)<br />

prove a number <strong>of</strong> limit theorems for sums <strong>of</strong> exchangeable random variables.<br />

A quote from the Preface <strong>of</strong> Gnedenko and Kolmogorov (1954) is appropriate:<br />

In the formal construction <strong>of</strong> a course in the theory <strong>of</strong> probability,<br />

limit theorems appear as a kind <strong>of</strong> superstructure over elementary<br />

chapters, in which all problems have finite purely arithmetical character.<br />

In reality, however, the epistemological value <strong>of</strong> the theory <strong>of</strong><br />

probability is revealed only by limit theorems. Moreover, without limit<br />

theorems it is impossible to understand the real content <strong>of</strong> the primary<br />

concept <strong>of</strong> all our sciences — the concept <strong>of</strong> probability. In fact, all<br />

epistemologic value <strong>of</strong> the theory <strong>of</strong> probability is based on this: that<br />

large-scale random phenomena in their collective action create strict,<br />

nonrandom regularity. The very concept <strong>of</strong> mathematical probability<br />

would be fruitless if it did not find its realization in the frequency <strong>of</strong><br />

occurrence <strong>of</strong> events under large-scale repetition <strong>of</strong> uniform conditions<br />

....<br />

<strong>Theory</strong> <strong>of</strong> <strong>Statistics</strong> c○2000–2013 James E. Gentle

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