Scatter Graphs
SUCCESS CRITERIA: Where are you now?
Tick what you currently know about scatter graphs in the table below (one tick in
each row please):
Level Learning outcomes
C3
Can I plot points on a scatter
graph?
C2
Can I describe the relationship
between the data, including
correlation?
C1
Can I draw and use a "line of best
fit" to estimate results?
R
A
G
What are scatter graphs?
Scatter graphs show the relationship between two sets of data. Points are plotted
very like co-ordinates.
Below are the marks of eight students in their Maths and Science tests.
Student
A
B
C
D
E
F
G
H
Maths mark
56
73
51
62
24
67
94
35
Science mark
62
68
45
68
35
73
88
32
Draw a scatter graph of this information:
Student
A
B
C
D
E
F
G
H
Maths mark
56
73
51
62
24
67
94
35
Science mark 62
68
45
68
35
73
88
32
100
90
80
Science mark
70
60
50
40
30
20
10
0
10
20
30
40
50
60
Maths mark
70
80
90
100
Draw a scatter graph of this information:
Student
A
B
C
D
E
F
G
H
Maths mark
56
73
51
62
24
67
94
35
Science mark 62
68
45
68
35
73
88
32
What yours should look
like:
100
90
80
Science mark
70
60
50
40
30
20
10
0
10
20
30
40
50
60
Maths mark
70
80
90
100
Plot these sets of data on scatter graphs:
The data below shows the number of scarves sold by a shop in a week and the
temperature that day:
Day of the week
M
T
W
T
F
S
S
Sales of scarves
73
56
54
38
7
39
82
Temperature (oC)
9
13
15
19
25
12
5
The data below shows the amount of petrol used by a car and the distance driven on eight
different journeys:
Journey
1
2
3
4
5
6
7
8
Distance (km)
75
140
237
180
20
93
104
42
Petrol used (l)
7
12.5 25.3 16
3.5
8.9
9.5
4.1
How your scatter graph should look:
Day of the week M
T
W
T
F
S
S
Sales of
scarves
Temperature
(oC)
20
73
56
54
38
7
39
82
9
13
15
19
20
12
5
Temperature (oC)
15
10
5
0
10
20
30
40
50
60
Sales of scarves
70
80
90
100
How your scatter graph should look:
Journey
1
2
3
4
Distance (km) 75
140 197
Petrol used (l) 7
12.5 21.3 16
5
180 20
3.5
6
7
93
104 42
8.9
9.5
25
Petrol used (l)
20
15
10
5
0
20
40
60
80 100 120 140 160 180 200
Distance (km)
8
4.1
Scatter Graphs
SUCCESS CRITERIA: Where are you now?
Colour in where you now are with your understanding of plotting scatter graphs:
Level Learning outcomes
C3
Can I plot points on a scatter
graph?
C2
Can I describe the relationship
between the data, including
correlation?
C1
Can I draw and use a "line of best
fit" to estimate results?
R
A
G
What would you expect to
happen?
Look at the situations below and describe what you think might happen in each
case:
1. The sales of ice creams as the temperature rises during the summer.
2. The value of a mobile phone as it gets older.
3. The amount you'll get in a maths test the further you live from school.
What do scatter graphs tell us?
Scatter graphs show the relationship between our two sets of data.
We describe this relationship using correlation.
There are basically 3 types of correlation:
Positive, Negative and No Correlation
The more in line the
points, the stronger the
correlation.
What do you think the correlation might be in these
situations?
1. The sales of ice creams as the temperature rises during the summer.
2. The value of a mobile phone as it gets older.
3. The amount you'll get in a maths test the further you live from school.
Describe the correlation of these scatter graphs:
Draw a scatter graph of this information and describe the
correlation:
Student
A
B
C
D
E
F
G
H
Maths mark
56
73
51
62
24
67
94
35
Art mark
54
43
47
44
82
31
18
87
100
90
80
Art mark
70
60
50
40
30
20
10
0
10
20
30
40
50
60
Maths mark
70
80
90
100
Draw a scatter graph of this information and describe the
correlation:
Student
A
B
C
D
E
F
G
H
Maths mark
56
73
51
62
24
67
94
35
Art mark
54
43
47
44
82
31
18
87
100
90
80
Art mark
70
Correlation:
Negative(Moderate)
60
50
40
30
20
10
0
10
20
30
40
50
60
Maths mark
70
80
90
100
Scatter Graphs
SUCCESS CRITERIA: Where are you now?
Colour in where you now are with your understanding of describing correlation:
Level Learning outcomes
C3
Can I plot points on a scatter
graph?
C2
Can I describe the relationship
between the data, including
correlation?
C1
Can I draw and use a "line of best
fit" to estimate results?
R
A
G
How do we use scatter graphs?
We can use scatter graphs to estimate results based upon other results. We do this by
drawing a "line of best fit".
A "line of best fit" is a straight line (drawn with a ruler) that goes through the middle of
your points. This is an estimate, but try to get half of the points on either side of it.
The "line of best fit" does not have to go through the origin!
When doing an estimate from a scatter graph you must draw the "line of best fit" or you
will get no marks!
If there is no correlation, you cannot draw a "line of best fit".
A typical exam question:
Imogen missed the Science test because she was ill.
She sat the Maths test and got 85.
Use your scatter graph to estimate what Imogen would have achieved on the Science test.
100
90
80
Science mark
70
60
50
40
30
20
10
0
10
20
30
40
50
60
Maths mark
70
80
90
100
A typical exam question:
Imogen missed the Science test because she was ill.
She sat the Maths test and got 85.
Use your scatter graph to estimate what Imogen would have achieved on the Science test.
100
90
80
Science mark
70
Imogen would
have got 83.
60
50
40
30
20
10
0
10
20
30
40
50
60
Maths mark
70
80
90
100
Estimate, using your graph, how many
scarves the shop would sell when the
temperature was 7oC.
Estimate, using your graph, how many
litres of petrol the car would use on a
journey of 160km.
20
25
20
Petrol used (l)
10
Temperature (oC)
15
15
10
5
5
0
10
20
30
40
50
60
Sales of scarves
70
80
90
100
0
20
40
60
80 100 120 140 160 180 200
Distance (km)
Estimate, using your graph, how many
scarves the shop would sell when the
temperature was 7oC.
Estimate, using your graph, how many
litres of petrol the car would use on a
journey of 160km.
20
25
20
Petrol used (l)
10
Temperature (oC)
15
15
10
5
5
0
10
20
30
40
50
60
70
Sales of scarves
Answer: 80 scarves
80
90
100
0
20
40
60
80 100 120 140 160 180 200
Distance (km)
Answer: 15 litres
Scatter Graphs
SUCCESS CRITERIA: Where are you now?
Colour in where you now are with your understanding of using "lines of best fit" to
estimate results:
Level Learning outcomes
C3
Can I plot points on a scatter
graph?
C2
Can I describe the relationship
between the data, including
correlation?
C1
Can I draw and use a "line of best
fit" to estimate results?
R
A
G
Now try some exam questions!