| Exam Board | Edexcel |
|---|---|
| Module | S2 (Statistics 2) |
| Marks | 9 |
| Paper | Download PDF ↗ |
| Mark scheme | Download PDF ↗ |
| Topic | Modelling and Hypothesis Testing |
| Type | Distribution selection for modeling |
| Difficulty | Easy -1.2 This is a straightforward distribution-matching question requiring recall of standard probability models (Poisson for rare events, continuous uniform for remainders, binomial for fixed trials). No calculations or problem-solving needed—just recognition of textbook scenarios, making it easier than average. |
| Spec | 2.04b Binomial distribution: as model B(n,p)5.02i Poisson distribution: random events model5.04a Linear combinations: E(aX+bY), Var(aX+bY) |
| Answer | Marks | Guidance |
|---|---|---|
| (a) Poisson; e.g. J occurs singly, at random, at constant rate | B1 B2 | |
| (b) continuous uniform; e.g. initial lengths random \(\therefore\) equal chance of any length 0 to 3 left over | B1 B2 | |
| (c) binomial; e.g. fixed no. of spins, two outcomes, fixed prob. of head | B1 B2 | (9 marks total) |
(a) Poisson; e.g. J occurs singly, at random, at constant rate | B1 B2 |
(b) continuous uniform; e.g. initial lengths random $\therefore$ equal chance of any length 0 to 3 left over | B1 B2 |
(c) binomial; e.g. fixed no. of spins, two outcomes, fixed prob. of head | B1 B2 | (9 marks total)
---2. Suggest, with reasons, suitable distributions for modelling each of the following:
\begin{enumerate}[label=(\alph*)]
\item the number of times the letter J occurs on each page of a magazine,
\item the length of string left over after cutting as many 3 metre long pieces as possible from partly used balls of string,
\item the number of heads obtained when spinning a coin 15 times.
\end{enumerate}
\hfill \mbox{\textit{Edexcel S2 Q2 [9]}}