| Exam Board | CAIE |
|---|---|
| Module | S2 (Statistics 2) |
| Year | 2020 |
| Session | Specimen |
| Marks | 4 |
| Paper | Download PDF ↗ |
| Topic | Approximating the Poisson to the Normal distribution |
| Type | Simple probability using normal approximation |
| Difficulty | Standard +0.3 This is a straightforward application of the normal approximation to Poisson with continuity correction. Students need to recognize λ=4, apply the approximation N(4,4), use continuity correction for P(4≤X≤9) → P(3.5<Y<9.5), and standardize. It's slightly easier than average as it's a direct textbook procedure with clear parameters given, requiring only routine application of a standard technique. |
| Spec | 2.04d Normal approximation to binomial5.02i Poisson distribution: random events model |
The number of calls received at a large call centre has a Poisson distribution with mean 4 calls per 5 minute period.
\begin{enumerate}[label=(\alph*)]
\item[(c)] Use an approximation to find the probability that the number of calls received in a 5 minute period is between 4 and 9 inclusive. [4]
\end{enumerate}
\hfill \mbox{\textit{CAIE S2 2020 Q3 [4]}}