Ch. 10 Correlation and Regression 10-1 Notes Scatter Diagrams and Linear Correlation.
Scatter Diagrams Part One: Drawing Them. Lesson Objective To be able to draw a Scatter Diagram.
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Scatter Diagrams Part One: Drawing Them
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Transcript of Scatter Diagrams Part One: Drawing Them. Lesson Objective To be able to draw a Scatter Diagram.
Scatter Diagrams
Part One: Drawing Them
Lesson Objective
• To be able to draw a Scatter Diagram
Scatter Diagrams
A Scatter Diagram is a graph of unconnected points
When drawing graphs, we must remember to do the following things:
1. Always give the graph a title
2. Always label both axis, including correct units
3. Choose a sensible scale
4. Plot your points carefully (x first, y second)
Pints of lager Mr. X has on a Saturday night
5 8 9 1 4 4 7 12 6 0
Number of books he marks on a Sunday
morning40 25 22 60 38 34 22 1 31 70
Number of goals PNE concede at the
weekend1 3 0 1 2 5 0 0 4 5
Number of pupils I put in detention on
Monday2 6 0 3 5 10 1 0 7 12
Temperature in Alaska, Canada (degrees
Celsius)5 -3 -5 10 8 -20 -6 8 -15 9
Money in my bank account (£)
20 31 6 7 22 15 220 -10 -100 -220
A graph to show the relationship between pints of lager drunk and books marked
0
20
40
60
80
0 5 10 15
pints of lager
boo
ks m
arke
d
A graph to show the realtionship between the number of goals PNE concede at the number of pupils I put in
detention
0
5
10
15
0 1 2 3 4 5 6
goals conceded
pupi
ls in
det
enti
on
A graph to show the relationship between the temperature in Alaska and the money in my bank
-300
-200
-100
0
100
200
300
-30 -20 -10 0 10 20
temperature in Alaska (degrees Celcius)
mon
ey in
ym
ban
k (£
)
Scatter Diagrams
Part Two: Interpreting Them
Lesson Objective
• To be able to interpret Scatter Diagrams
• To understand the terms Correlation and the Line of Best Fit
A graph to show the relationship between pints of lager drunk and books marked
0
20
40
60
80
0 5 10 15
pints of lager
boo
ks m
arke
d
A graph to show the relationship between pints of lager drunk and books marked
0
20
40
60
80
0 5 10 15
pints of lager
boo
ks m
arke
d
A graph to show the realtionship between the number of goals PNE concede at the number of pupils I put in
detention
0
5
10
15
0 1 2 3 4 5 6
goals conceded
pupi
ls in
det
enti
on
A graph to show the realtionship between the number of goals PNE concede at the number of pupils I put in
detention
0
5
10
15
0 1 2 3 4 5 6
goals conceded
pupi
ls in
det
enti
on
A graph to show the relationship between the temperature in Alaska and the money in my bank
-300
-200
-100
0
100
200
300
-30 -20 -10 0 10 20
temperature in Alaska (degrees Celcius)
mon
ey in
ym
ban
k (£
)
A graph to show the relationship between the temperature in Alaska and the money in my bank
-300
-200
-1000
100
200
300
-30 -20 -10 0 10 20
temperature in Alaska (degrees Celcius)
mon
ey in
ym
ban
k (£
)
• The relationship between two variables is called a Correlation
• A line of best-fit is a line which helps us to identify the type of correlation (positive, negative, no correlation) & make predictions
• The line of best fit is drawn so that the points are evenly distributed on either side of the line
• The closer the dots to the line, the stronger the correlation
Remember:
1. The line of best fit is a STRAIGHT LINE
2. It DOES NOT have to pass through the origin
3. It DOES NOT have to go through each point
Interpreting Scatter Diagrams
Correlation can be strong or weak
Strong Positive Correlation
All the points lie close to the line of best fit
Weak Positive Correlation
The points are well spread out from the line of best fit but still follow the trend
A bit of work…
Exercise 10:2B, Page 229Q1 - 3
