Scatter Diagrams

1
Scatter Diagrams

• Part One Drawing Them

2
Lesson Objective

• To be able to draw a Scatter Diagram

3

• Scatter Diagrams
• A Scatter Diagram is a graph of unconnected
  points
• When drawing graphs, we must remember to do the
  following things
• Always give the graph a title
• Always label both axis, including correct units
• Choose a sensible scale
• Plot your points carefully (x first, y second)

4
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 morning 40 25 22 60 38 34 22 1 31 70
Number of goals PNE concede at the weekend 1 3 0 1 2 5 0 0 4 5
Number of pupils I put in detention on Monday 2 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
5
(No Transcript)
6
(No Transcript)
7
(No Transcript)
8
Scatter Diagrams

• Part Two Interpreting Them

9
Lesson Objective

• To be able to interpret Scatter Diagrams
• To understand the terms Correlation and the Line
  of Best Fit

10
(No Transcript)
11
(No Transcript)
12
(No Transcript)
13
(No Transcript)
14
(No Transcript)
15
(No Transcript)
16
Interpreting Scatter Diagrams

• 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
• The line of best fit is a STRAIGHT LINE
• It DOES NOT have to pass through the origin
• It DOES NOT have to go through each point

17
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
18
A bit of work

• Exercise 102B, Page 229

Q1 - 3