| Exam Board | Edexcel |
|---|---|
| Module | S3 (Statistics 3) |
| Year | 2016 |
| Session | June |
| Marks | 6 |
| Paper | Download PDF ↗ |
| Mark scheme | Download PDF ↗ |
| Topic | Non-parametric tests |
| Type | Stratified sampling methods |
| Difficulty | Easy -1.2 This is a straightforward sampling methods question requiring only recall and application of standard definitions. Part (a) asks for obvious sources of bias (time/day, self-selection), part (b) is a textbook description of stratified sampling procedure with simple proportional calculations, and part (c) requires stating a standard advantage (randomness). No mathematical complexity or problem-solving insight needed. |
| Spec | 2.01c Sampling techniques: simple random, opportunity, etc2.01d Select/critique sampling: in context |
| Office location | Number of employees |
| Bristol | 856 |
| Dudley | 429 |
| Glasgow | 1215 |
3. A company wants to survey its employees' attitudes to work. The company's workforce is located at three offices. The number of employees at each location is summarised in the table below.
\begin{center}
\begin{tabular}{ | c | c | }
\hline
Office location & Number of employees \\
\hline
Bristol & 856 \\
\hline
Dudley & 429 \\
\hline
Glasgow & 1215 \\
\hline
\end{tabular}
\end{center}
Each employee is located at only one office.
A personnel assistant plans to survey the first 50 employees who arrive for work at the Bristol office on a Monday morning.
\begin{enumerate}[label=(\alph*)]
\item Give two reasons why this survey is likely to lead to a biased response.
A personnel manager has access to the company's information system that holds details of each employee including their place of work.
The manager decides to take a stratified sample of 150 employees.
\item Describe how to choose employees for this stratified sample.
\item Explain an advantage of using a stratified sample rather than a quota sample.
\end{enumerate}
\hfill \mbox{\textit{Edexcel S3 2016 Q3 [6]}}