Introduction to Probability · Problem 8.1.17

Law of Large Numbers — Grinstead & Snell

Mathematics — Probability · weierstrass-approximation

Problem

Let us toss a biased coin that comes up heads with probability pp and assume the validity of the Strong Law of Large Numbers as described in Exercise 15. Then, with probability 1, Snn→p\frac{S_n}{n} \to p as n→∞n \to \infty. If f(x)f(x) is a continuous function on the unit interval, then we also have f(Snn)→f(p).f\left(\frac{S_n}{n}\right) \to f(p). Finally, we could hope that E(f(Snn))→E(f(p))=f(p).E\left(f\left(\frac{S_n}{n}\right)\right) \to E(f(p)) = f(p). Show that, if all this is correct, as in fact it is, we would have proven that any continuous function on the unit interval is a limit of polynomial functions. This is a sketch of a probabilistic proof of an important theorem in mathematics called the Weierstrass approximation theorem.

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