Scatter graphs

The Maths Habit Handout to print

When ice cream sales go up, so do shark attacks.
Does ice cream cause shark attacks?

No: hot weather causes both

Correlation
The link between two sets of data.
Line of best fit
A straight line that follows the trend of the points.

Plot the points. Describe the correlation.

Hours of sunIce creams sold
215
422
530
738
841
1052

Puppies: age and mass. Estimate the mass at 7 weeks.

Age (weeks)2345689
Mass (kg)1.52.22.63.43.85.15.6
(a) plot the points
(b) correlationpositive
(c) estimateabout 4.5 kg

Tickets: price and number sold. Estimate the sales at £7.

Price (£)235689
Tickets sold948167544027
(a) plot the points
(b) correlationnegative
(c) estimateabout 47

Puppies: age and mass. Estimate the mass at 7 weeks.

Age (weeks)2345689
Mass (kg)1.52.22.63.43.85.15.6
(a) plot the points
(b) correlationpositive
(c) estimateabout 4.5 kg

Piano: hours of practice and mistakes. Estimate the mistakes after 6 hours.

Hours124578
Mistakes3129191793
(a) plot the points
(b) correlationnegative
(c) estimateabout 12

Puppies: age and mass. Estimate the mass at 7 weeks.

Age (weeks)2345689
Mass (kg)1.52.22.63.43.85.15.6
(a) plot the points
(b) correlationpositive
(c) estimateabout 4.5 kg

Sunflowers: age and height. Estimate the height at 25 days.

Age (days)51015203035
Height (cm)122533487081
(a) plot the points
(b) correlationpositive
(c) estimateabout 58 cm

Puppies: age and mass. Estimate the mass at 7 weeks.

Age (weeks)2345689
Mass (kg)1.52.22.63.43.85.15.6
(a) plot the points
(b) correlationpositive
(c) estimateabout 4.5 kg

Phones: age and battery life. Estimate the battery life at 4 years.

Age (years)123567
Battery (hours)20181713129
(a) plot the points
(b) correlationnegative
(c) estimateabout 15 hours

Puppies: age and mass. Estimate the mass at 7 weeks.

Age (weeks)2345689
Mass (kg)1.52.22.63.43.85.15.6
(a) plot the points
(b) correlationpositive
(c) estimateabout 4.5 kg

Revision: hours and test score. Estimate the hours for a score of 60.

Hours124578
Score324150587176
(a) plot the points
(b) correlationpositive
(c) estimateabout 5.5 hours

Scatter graphs worksheet, page 1

Scatter graphs worksheet, page 2

Answer sheet

  1. The puppy data runs from 2 to 9 weeks. Why not use it to estimate the mass at 40 weeks?

    40 weeks is outside the data

  2. Ice cream sales and shark attacks have positive correlation. Explain why one does not cause the other.

    Hot weather makes both go up

  3. A scatter graph shows height against maths test score for a Year 10 class. What type of correlation would you expect? Why?

    None: height has no link to the score

  1. Describe the correlation shown by the scatter graph.

    Negative
    01020304050Hot drinks sold048121620Temperature (°C)

  2. Draw a line of best fit. Use it to estimate the drinks sold at 12 °C.

    about 28 (26 to 30)

  3. Explain why the graph should not be used to estimate the drinks sold at 35 °C.

    35 °C is outside the data
Exit tickets to print