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Scatter Graphs & Correlation Practice Questions

Question 1

4 marks

The table shows the maximum temperature, in °C, and the number of ice creams sold at a seaside kiosk on each of ten days.

Maximum temperature (°C) 14 16 17 19 20 21 23 24 26 27
Number of ice creams sold 40 50 45 60 65 70 80 75 90 95

The first six points have been plotted on the scatter graph below.

1214161820222426282030405060708090100Maximum temperature (°C)Number of ice creams sold

(a)

Complete the scatter graph to show the information for the last four days.

(b)

Write down the type of correlation shown by the scatter graph.

(c)

Write down a sentence describing the relationship between the maximum temperature and the number of ice creams sold.

Question 2

3 marks

The scatter diagram shows information about 12 pupils in Year 9. It shows the time each pupil spent playing computer games in one week and the pupil's score in a spelling test.

024681012141601020304050Time playing computer games (hours)Spelling test score

(a)

One of the points is an outlier.

Write down the coordinates of this point.

(b)

For all the other points, write down the type of correlation.

(c)

A teacher says,

"Pupils who spent longer playing computer games tended to get lower spelling test scores."

Does the scatter diagram support what the teacher says? Give a reason for your answer.

Question 3

4 marks
(a)

For each pair of variables below, write down the type of correlation you would expect.

(i) the age of a young child and the number of words the child can read

(ii) the outside air temperature and the amount of gas used to heat a house

(iii) the length of a person's hair and the length of that person's foot

(b)

Marcus collects data for each day of one summer. He finds that there is a strong positive correlation between the number of ice creams sold in his town and the number of people treated for sunburn.

Marcus says,

"This shows that eating ice cream causes sunburn."

Explain why Marcus may be wrong.