| Exam Board | Edexcel |
|---|---|
| Module | S2 (Statistics 2) |
| Marks | 7 |
| Paper | Download PDF ↗ |
| Topic | Approximating the Poisson to the Normal distribution |
| Type | State condition for normal approximation |
| Difficulty | Moderate -0.8 This is a straightforward S2 question testing standard bookwork (stating λ ≥ 10 or similar) and routine application of normal approximation with continuity correction. Part (a) is pure recall, part (b) follows a standard algorithm (apply continuity correction, standardize, use tables). No problem-solving or insight required, making it easier than average A-level questions. |
| Spec | 2.04e Normal distribution: as model N(mu, sigma^2)2.04f Find normal probabilities: Z transformation5.02i Poisson distribution: random events model5.02j Poisson formula: P(X=x) = e^(-lambda)*lambda^x/x!5.02k Calculate Poisson probabilities |
\begin{enumerate}[label=(\alph*)]
\item Write down the condition needed to approximate a Poisson distribution by a Normal distribution. [1]
\end{enumerate}
The random variable Y ~ Po(30).
\begin{enumerate}[label=(\alph*)]
\setcounter{enumi}{1}
\item Estimate P(Y > 28). [6]
\end{enumerate}
\hfill \mbox{\textit{Edexcel S2 Q2 [7]}}