Home / CIE iGCSE Maths C9.5 Scatter diagrams Exam Style Practice Questions- Paper 3

CIE iGCSE Maths C9.5 Scatter diagrams Exam Style Practice Questions- Paper 3

IGCSE Mathematics(0580) Practice Questions Paper 3 - All Chapters

Question

A school records the marks students score in Paper 1 and Paper 2 of a subject.
The scatter diagram shows the scores for twelve students.

(a) What type of correlation is shown in the scatter diagram?

(b) On the scatter diagram, draw a line of best fit.

(c) Another student scores 35 on Paper 1.
Use your line of best fit to find an estimate for their score on Paper 2.

Most-appropriate topic codes (Cambridge IGCSE Mathematics 0580):

• C9.5 Scatter diagrams
▶️ Answer/Explanation

(a)
The points on the graph generally slope upwards from left to right, meaning as the score on Paper 1 increases, the score on Paper 2 also increases.
✅ Answer: positive

(b)
A line of best fit should be drawn with a ruler straight through the middle of the scatter points, following the general trend and leaving roughly equal numbers of points on either side.

✅ Answer: Acceptable ruled line of best fit drawn.

(c)
By reading off the graph at $x = 35$ (Paper 1), follow vertically up to your drawn line of best fit and read horizontally across to the y-axis (Paper 2). Due to minor drawing variations, a small range is acceptable.
✅ Answer: 42 to 47 (Based on your line of best fit)

Question

Fidel gives different amounts of water to some plants.

The scatter diagram shows the height (cm) and the amount of water (ml) for each of 15 plants.

(a) Plot these two results on the scatter diagram.

(b) What type of correlation is shown in the scatter diagram?

(c) One of the plants had a lower height than expected for the amount of water given. On the scatter diagram, put a ring around the point for this plant.

(d) (i) On the scatter diagram, draw a line of best fit.

(ii) Another plant is given 65 ml of water. Use your line of best fit to estimate the height of this plant.

(e) Find the percentage of these 17 plants that have a height of more than 24 cm. Give your answer correct to 1 decimal place.

▶️ Answer/Explanation
Solution

(a) Ans: Two points accurately plotted

The points (40, 15) and (80, 35) are plotted on the scatter diagram.

(b) Ans: Positive

The scatter diagram shows an upward trend, indicating a positive correlation between water given and plant height.

(c) Ans: (60, 7) indicated

The point (60, 7) is circled as it lies significantly below the general trend.

(d)(i) Ans: Accurate straight line of best fit

A straight line is drawn passing through the middle of the data points, minimizing the distance from all points.

(d)(ii) Ans: 24 to 32

Using the line of best fit, for 65 ml of water, the estimated height is between 24 cm and 32 cm.

(e) Ans: 47.1

Out of 17 plants, 8 have heights > 24 cm. The percentage is calculated as $\left(\frac{8}{17}\right) \times 100 \approx 47.1\%$.

Visualizations:

(a)

(b)

(c)

(d)(i)

(d)(ii)

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