| Exam Board | Edexcel |
|---|---|
| Module | S3 (Statistics 3) |
| Marks | 4 |
| Paper | Download PDF ↗ |
| Mark scheme | Download PDF ↗ |
| Topic | Combinations & Selection |
| Type | Calculating stratified sample sizes |
| Difficulty | Easy -1.2 This is a straightforward stratified sampling question requiring only proportional allocation calculations (dividing each stratum size by total population then multiplying by sample size) and recall of advantages. No problem-solving or conceptual depth required—purely mechanical arithmetic and standard textbook knowledge. |
| Spec | 2.01c Sampling techniques: simple random, opportunity, etc |
| Answer | Marks | Guidance |
|---|---|---|
| (a) total = 500 ∴ require \(\frac{1}{5}\) giving 33, 28, 21, 18 respectively | M1, A1 | |
| (b) e.g. know that each group is represented proportionally for each strata as well for whole | B2 | (4) |
**(a)** total = 500 ∴ require $\frac{1}{5}$ giving 33, 28, 21, 18 respectively | M1, A1 |
**(b)** e.g. know that each group is represented proportionally for each strata as well for whole | B2 | (4) |
---\begin{enumerate}
\item A Veterinary Surgeon wishes to survey a stratified sample of size 100 from those people who have pets registered at her surgery. The list below shows the strata to be used and the number in each group.
\end{enumerate}
\begin{itemize}
\item people who own just dogs - 165 ,
\item people who own just cats - 140 ,
\item people who own just small mammals - 105,
\item others, including those who own more than one type of pet - 90 .\\
(a) Find how many members of each group should be included in the sample.\\
(b) Give two advantages of using stratified sampling.
\end{itemize}
\hfill \mbox{\textit{Edexcel S3 Q1 [4]}}