| Exam Board | OCR |
|---|---|
| Module | PURE |
| Marks | 4 |
| Paper | Download PDF ↗ |
| Topic | Bivariate data |
| Type | Interpret or describe given scatter diagram |
| Difficulty | Easy -1.8 Part (a) requires only basic interpretation of a scatter diagram (negative correlation), and part (b) is straightforward calculation of mean and standard deviation from given data using standard formulas. Both are routine recall/application with no problem-solving required, making this significantly easier than average A-level questions. |
| Spec | 2.02c Scatter diagrams and regression lines2.02d Informal interpretation of correlation2.02g Calculate mean and standard deviation |
| Answer | Marks | Guidance |
|---|---|---|
| Answer | Marks | Guidance |
| Negative correlation between hours and money stated or implied, e.g. "Time spent on earning reduces time on school work" | B1 | Must be in context |
| Except for one student (or one point) or There is an outlier or anomaly oe or Small sample so unreliable | B1 | Allow without context. Or "Poor (or no) correlation between hours and money B1 because of the outlier B1" |
| [2] |
| Answer | Marks | Guidance |
|---|---|---|
| Answer | Marks | Guidance |
| Mean \(= 28.9\) | B1 | Allow 28.8; cao; Ignore all else |
| \(SD = 7.93\) (3 sf) | B1 [2] |
## Question 8(a):
| Answer | Marks | Guidance |
|--------|-------|----------|
| Negative correlation between hours and money stated or implied, e.g. "Time spent on earning reduces time on school work" | B1 | Must be in context |
| Except for one student (or one point) or There is an outlier or anomaly oe or Small sample so unreliable | B1 | Allow without context. Or "Poor (or no) correlation between hours and money B1 because of the outlier B1" |
| **[2]** | | |
## Question 8(b):
| Answer | Marks | Guidance |
|--------|-------|----------|
| Mean $= 28.9$ | B1 | Allow 28.8; cao; Ignore all else |
| $SD = 7.93$ (3 sf) | B1 [2] | |
---8 A random sample of 10 students from a college was chosen. They were asked how much time, $x$ hours, they spent studying, and how much money, $\pounds y$, they earned, in a typical week during term time. The results are shown in the scatter diagram.\\
\includegraphics[max width=\textwidth, alt={}, center]{c4cc2cd8-46bf-448f-b223-92378984bfde-5_544_741_555_242}
\begin{enumerate}[label=(\alph*)]
\item Comment on the relationship shown by the diagram between hours spent studying and money earned, during term time, by these 10 students.
The coordinates of the points in the diagram are $( 18,23 ) , ( 20,21 ) , ( 23,20 ) , ( 25,19 ) , ( 25,21 )$, $( 27,18 ) , ( 32,16 ) , ( 38,17 ) , ( 40,16 )$ and $( 41,23 )$.
\item Find the mean and standard deviation of the number of hours spent per week studying during term time by these 10 students.
\end{enumerate}
\hfill \mbox{\textit{OCR PURE Q8 [4]}}