

\subsection{\bf 2.2\hspace{1em} Birth and Death}
\subsection{\bf Processes Overview---I}

\begin{slide}
\begin{itemize}
\item We will briefly sketch some techniques which at their most
elementary, justify Poisson for a counting experiment.

\item The more advanced applications are important in many practical
problems (telephones (random calls) and biology (random birth/deaths)),
involving happenings distributed more or less randomly in times.

\item We start with a discrete (as opposed to continuous) example:
Telephone calls.

\item Suppose your favorite secretary receives $N$ telephone calls in
an hour.

\item We wish to find the probability that she received $k$ calls in a
given time $t$
\end{itemize}
\end{slide}
