| Exam Board | OCR MEI |
|---|---|
| Module | Paper 2 (Paper 2) |
| Session | Specimen |
| Marks | 4 |
| Paper | Download PDF ↗ |
| Mark scheme | Download PDF ↗ |
| Topic | Bivariate data |
| Type | Hypothesis test for correlation |
| Difficulty | Moderate -0.8 This is a straightforward hypothesis testing question requiring only interpretation of given values against critical values (part a) and basic commentary on scatter diagram features (part b). No calculations needed, just recall of hypothesis test conclusions and recognition of scatter diagram patterns. Significantly easier than average A-level questions which typically require multi-step calculations or derivations. |
| Spec | 5.08a Pearson correlation: calculate pmcc5.08d Hypothesis test: Pearson correlation |
| Answer | Marks | Guidance |
|---|---|---|
| 9 | (a) | p |
| Answer | Marks |
|---|---|
| population) [2] | M1 |
| Answer | Marks |
|---|---|
| [2] | 1.1 |
| 2.2b | Oe but not evidence of positive |
| Answer | Marks | Guidance |
|---|---|---|
| 9 | (b) | E.g. diagram shows positive correlation overall, but |
| Answer | Marks |
|---|---|
| correlation | B1 |
| Answer | Marks |
|---|---|
| [2] | 2.3 |
| 2.2b | Accept other suitable correct |
Question 9:
9 | (a) | p
0.758 > 0.279 S
So there is sufficient evidence of correlation (in the
population) [2] | M1
A1
[2] | 1.1
2.2b | Oe but not evidence of positive
correlation.
9 | (b) | E.g. diagram shows positive correlation overall, but
the data consists of two distinct clusters.
E.g. neither of the two clusters show evidence of
correlation | B1
B1
[2] | 2.3
2.2b | Accept other suitable correct
commentsA geyser is a hot spring which erupts from time to time. For two geysers, the duration of each eruption, $x$ minutes, and the waiting time until the next eruption, $y$ minutes, are recorded.
\begin{enumerate}[label=(\alph*)]
\item For a random sample of 50 eruptions of the first geyser, the correlation coefficient between $x$ and $y$ is 0.758.
The critical value for a 2-tailed hypothesis test for correlation at the 5% level is 0.279.
Explain whether or not there is evidence of correlation in the population of eruptions. [2]
\end{enumerate}
The scatter diagram in Fig. 9 shows the data from a random sample of 50 eruptions of the second geyser.
\includegraphics{figure_9}
\begin{enumerate}[label=(\alph*)]
\setcounter{enumi}{1}
\item Stella claims the scatter diagram shows evidence of correlation between duration of eruption and waiting time. Make two comments about Stella's claim. [2]
\end{enumerate}
\hfill \mbox{\textit{OCR MEI Paper 2 Q9 [4]}}