Suppose that a box contains \( N \) balls, of which \(
\textcolor{red}{M} \) are red ("success") and \( \textcolor{red}{N-M}
\) are of another color ("failure"). We now draw balls with replacement
(notably, if we draw without replacement, we would end up with
hypergeometric
distribution), so
that after each draw the selected ball is returned to the box before the
next draw. Consequently, each draw is independent, and the probability of
success remains constant,
\begin{equation}
p=\frac{M}{N}.
\end{equation}
Let \( Y \) denote the number of red balls drawn ("successes") in the
\( n \) draws ("experiments"). We wish to determine the probability that
exactly \( \textcolor{red}{k} \) of the \( n \) (all) draws are
successes.