# Question 4:

## Part (a)(i):
| Answer | Marks | Guidance |
|--------|-------|----------|
| $r = -0.326$ to $-0.325$ | B3 | AWFW $(-0.32569)$ |
| $r = -0.33$ to $-0.32$ | (B2) | AWFW |
| $r = -0.4$ to $-0.2$ | (B1) | AWFW |
| $r = 0.2$ to $0.4$ | (B1) | AWFW |
| Attempt at $\sum x$, $\sum x^2$, $\sum y$, $\sum y^2$, $\sum xy$ **or** attempt at $S_{xx}$, $S_{yy}$, $S_{xy}$ | M1 | Values: 756, 50004, 738, 48200, 45652 (all 5 attempted); or 2376, 2813, $-842$ (all 3 attempted) |
| Attempt substitution into correct formula for $r$ | m1 | |
| $r = -0.326$ to $-0.325$ | A1 | AWFW |
| **Total** | **3** | |

## Part (a)(ii):
| Answer | Marks | Guidance |
|--------|-------|----------|
| Some/little/slight/(fairly/quite) weak / (fairly/quite) moderate **negative** (linear) correlation/relationship/association/link *(but not 'trend')* between **marks/percentages** in the two examination papers | Bdep1 | Dependent on $-0.4 \leq r \leq -0.2$; OE; must qualify strength and state negative; Bdep0 for 'low', 'small', 'poor', 'unlikely', 'medium', 'average', or adjective 'very' |
| Context mark | B1 | Context; providing $-1 < r < 1$ |
| **Total** | **2** | |

## Part (b)(i):
| Answer | Marks | Guidance |
|--------|-------|----------|
| Identifying linear/non-linear/multiple/no patterns *(allow 'trend')* **or** Identifying outliers/anomalies **or** Estimating/gives idea of value or sign of $r$ | B2,1 | OE; only one mark from each set; B0 for reference to **checking** calculated value |
| **Total** | **2** | |

## Part (b)(ii):
| Answer | Marks | Guidance |
|--------|-------|----------|
| Graph with 6 labelled points correct | B2 | Correct $\Rightarrow$ within circle of radius equal to distance between 2 grid lines |
| 5 or 4 labelled points correct | (B1) | Deduct 1 mark for any unlabelled or incorrectly labelled point |
| **Total** | **2** | |

## Part (b)(iii):
| Answer | Marks | Guidance |
|--------|-------|----------|
| Two separate correlations/relationships/lines/associations/links/sets of data *(but not 'trends')* | B1 | OE; eg A to F and G to L |
| **Total** | **1** | |

## Part (c):
| Answer | Marks | Guidance |
|--------|-------|----------|
| A to F: $(+)0.7$ to $(+)0.99$ | B1 | AWFW; allow calculation $(0.937)$; if not labelled, assume order A to F then G to L |
| G to L: $-0.9$ to $-0.5$ | B1 | AWFW; allow calculation $(-0.757)$ |
| **Total** | **2** | |

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