Correlation Prediction
1. **Problem Statement:**
We have a scatter diagram showing scores of 10 students in Maths (x-axis) and English (y-axis) exams.
(a) Identify the type of correlation shown by the graph.
(b) Predict the English score for a pupil who scored 60 in Maths but missed the English exam, using the line of best fit.
2. **Understanding Correlation:**
Correlation measures the relationship between two variables. It can be:
- Positive correlation: as one variable increases, the other also increases.
- Negative correlation: as one variable increases, the other decreases.
- No correlation: no clear pattern.
3. **Analyzing the Graph:**
The scatter plot shows points descending from near (10, 85) to (90, 25), indicating that as Maths scores increase, English scores decrease.
4. **Answer to (a):**
This is a **negative correlation** because the line of best fit slopes downward.
5. **Using the Line of Best Fit for Prediction:**
The line passes approximately through points (10, 85) and (90, 25).
6. **Find the equation of the line:**
Slope $m = \frac{25 - 85}{90 - 10} = \frac{-60}{80} = -\frac{3}{4}$.
Using point-slope form with point (10, 85):
$$y - 85 = -\frac{3}{4}(x - 10)$$
Simplify:
$$y = -\frac{3}{4}x + \frac{3}{4} \times 10 + 85 = -\frac{3}{4}x + 7.5 + 85 = -\frac{3}{4}x + 92.5$$
7. **Predict English score for Maths = 60:**
$$y = -\frac{3}{4} \times 60 + 92.5 = -45 + 92.5 = 47.5$$
8. **Interpretation:**
The predicted English score for the pupil who scored 60 in Maths is approximately **47.5**.
**Final answers:**
- (a) Negative correlation.
- (b) Predicted English score is approximately 47.5.