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Math 6010 • Linear Models

1994 • Question 6

Let \(0\leq X_n\leq 1\) be adapted to \(\mathcal{F}_n\). Let \(\alpha,\beta>0\) with \(\alpha+\beta=1\) and suppose \[ P(X_{n+1}=\alpha+\beta X_n\mid \mathcal{F}_n)=X_n \] \[ P(X_{n+1}=\beta X_n\mid \mathcal{F}_n)=1-X_n. \] **(a)** Show that \(P\{\lim_{n\to\infty}X_n=0\text{ or }1\}=1\). **(b)** Show that if \(X_0=\theta\), then \(P\{\lim_{n\to\infty}X_n=1\}=\theta\).

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Let \(0\leq X_n\leq 1\) be adapted to \(\mathcal{F}_n\). Let \(\alpha,\beta>0\) with \(\alpha+\beta=1\) and suppose
\[
P(X_{n+1}=\alpha+\beta X_n\mid \mathcal{F}_n)=X_n
\]
\[
P(X_{n+1}=\beta X_n\mid \mathcal{F}_n)=1-X_n.
\]
\begin{parts}
\item Show that \(P\{\lim_{n\to\infty}X_n=0\text{ or }1\}=1\).
\item Show that if \(X_0=\theta\), then \(P\{\lim_{n\to\infty}X_n=1\}=\theta\).
\end{parts}