1. Edexcel GCSE Maths Spec B – Modular: Booster C © Pearson Education 2010. This document may have been altered from the original. To understand how to approach a question about scatter diagrams. Objectives

2. Edexcel GCSE Maths Spec B – Modular: Booster C © Pearson Education 2010. This document may have been altered from the original. John is interested in finding out how sales at his ice cream van are related to the temperature outside. He records the takings in pounds and the temperature on several random summer days. The results are show in the scatter diagram below. Takings (£) Temperature (°C) a.Describe the correlation shown in the diagram. b.Draw a line of best fit. c.Estimate sales on a day when the temperature is 26.5°C. d.Give two reasons why should John not use the graph to estimate sales on a day when the temperature is 6°C.

3. Edexcel GCSE Maths Spec B – Modular: Booster C © Pearson Education 2010. This document may have been altered from the original. Takings (£) Temperature (°C) a.Describe the correlation shown in the diagram. The takings rise as the temperature does, so the correlation is strong and positive.

4. Edexcel GCSE Maths Spec B – Modular: Booster C © Pearson Education 2010. This document may have been altered from the original. Takings (£) Temperature (°C) b.Draw a line of best fit. Don’t continue the line beyond the points drawn. Try to place the line as close to as many points as possible.

5. Edexcel GCSE Maths Spec B – Modular: Booster C © Pearson Education 2010. This document may have been altered from the original. Takings (£) Temperature (°C) c.Estimate sales on a day when the temperature is 26.5°C. Find 26.5°C on the temperature axis and draw these lines. Roughly £560

6. Takings (£) Temperature (°C) d.Give two reasons why should John not use the graph to estimate sales on a day when the temperature is 6°C; 6°C is outside the range of the data. The pattern may change so we can’t use the diagram to make the estimate. Edexcel GCSE Maths Spec B – Modular: Booster C © Pearson Education 2010. This document may have been altered from the original.

7. Takings (£) Temperature (°C) Also, 6°C is not likely to be a temperature recorded in the summer, so we can’t use summer data to make an estimate. d.Give two reasons why should John not use the graph to estimate sales on a day when the temperature is 6°C; Edexcel GCSE Maths Spec B – Modular: Booster C © Pearson Education 2010. This document may have been altered from the original.

8. Always use a sharp pencil to draw lines on your diagrams. Summary Always show lines when making estimates using the graph. Never extend the line beyond the range of data that you have. Never make estimates beyond the range of the data in the diagram. Edexcel GCSE Maths Spec B – Modular: Booster C © Pearson Education 2010. This document may have been altered from the original.