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4024/12 May/Jun 2020, Question 8: Scatter Diagrams and Correlation

Cambridge O Level Mathematics 4024 · Paper 12 (Non-calculator) · Non-calculator · 3 marks

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The question, in short

Scatter graph of step counts against heights for 12 people walking 100 m; identify correlation type, add a best-fit line, and estimate steps for a 175 cm person.

Summarised in our own words. Use the official paper for the exact wording and the diagram.

Part (a) · 1 mark

State what kind of correlation the plotted points indicate.

  1. 1As height increases, the number of steps decreases
  2. 2Negative correlation

AnswerNegative

Part (b) · 1 mark

Add a straight best-fit line to the scatter graph.

  1. 1Draw one ruled straight line through the middle of the points, e.g. through about (150, 159) and (204, 116)

AnswerRuled line of best fit

Part (c) · 1 mark

Using your line, estimate the step count for someone 175 cm tall.

  1. 1Go up from 175 cm to the line, then across to the steps axis
  2. 2Line through (150, 159) and (204, 116): 159 − 25 × 43/54 ≈ 139
  3. 3About 139 steps

Answer136 to 140

Stuck on a step? Read the free lesson: Scatter Diagrams and Correlation

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