| Exam Board | OCR MEI |
|---|---|
| Module | S1 (Statistics 1) |
| Marks | 4 |
| Paper | Download PDF ↗ |
| Mark scheme | Download PDF ↗ |
| Topic | Binomial Distribution |
| Type | Single batch expected count |
| Difficulty | Easy -1.2 This is a straightforward binomial probability question requiring only direct application of the formula P(X=0) = (0.75)^6 and then multiplication by 50 for the expectation. It involves minimal steps, standard S1 content, and no problem-solving insight—purely routine calculation that's easier than average A-level questions. |
| Spec | 2.04b Binomial distribution: as model B(n,p)2.04c Calculate binomial probabilities |
| Answer | Marks | Guidance |
|---|---|---|
| (i) | P(X = 0) = 0.756 = 0.178 | M1 for 0.756 |
| A1 CAO | 2 | Or from tables 0.1780 Or 729/4096 |
| Answer | Marks | Guidance |
|---|---|---|
| (ii) | E(X) = np = 50 0.178 = 8.9 | M1 for product |
| A1 FT | 2 | FT their answer to (i) providing it’s a probability |
| Answer | Marks |
|---|---|
| TOTAL | 4 |
Question 4:
--- 4
(i) ---
4
(i) | P(X = 0) = 0.756 = 0.178 | M1 for 0.756
A1 CAO | 2 | Or from tables 0.1780 Or 729/4096
Allow 0.18 with working
(ii) | E(X) = np = 50 0.178 = 8.9 | M1 for product
A1 FT | 2 | FT their answer to (i) providing it’s a probability
NB A0 if subsequently rounded
TOTAL | 425% of the plants of a particular species have red flowers. A random sample of 6 plants is selected.
\begin{enumerate}[label=(\roman*)]
\item Find the probability that there are no plants with red flowers in the sample. [2]
\item If 50 random samples of 6 plants are selected, find the expected number of samples in which there are no plants with red flowers. [2]
\end{enumerate}
\hfill \mbox{\textit{OCR MEI S1 Q4 [4]}}