Graphs
Math 8
S
Introduction to types of graphs
S Graphs are pictures of data
S They can help you communicate your ideas
S We are going to identify advantages and disadvantages of
different types of graphs
Before we graph: gather data
S How many times did you use a vending machine last week?
Number of times using
vending machine
Number of students
0 times
5
1~4 times
8
5~9 times
4
10 or more times
1
Pictograph
0 times
1~4 times
5~9 times
10+ times
= 1 student
Pictograph
Advantages of Pictograph
Disadvantages of Pictograph
• Symbols are visually appealing
• Lengths of rows shows quick
comparison
• The key can be used to calculate
total numbers
• There may be a lot of symbols to
draw
• Difficult to read and draw partial
symbols
• Graph does not show percentage
of population
Circle Graph (pie chart)
6%
Number of students
28%
22%
44%
0 times
1~4 times
5~9 times
10 or more times
Circle Graph
Advantages
Disadvantages
• Shows parts of the whole
• Each part shows percent of
respondents
• Sizes of each part can be used to
compare responses
• Does not show the number of
respondents
• We cannot find out total number
of responses
• Difficult to draw accurately
Bar Graph
Students’ Vending Machine Usage
10
8
6
4
2
0
Number of Students
0 times
1~4 times 5~9 times 10 or more
times
Bar Graph
Advantages
Disadvantages
• Heights of the bars can be used to
compare responses
• The scale on the vertical axis can
be used to calculate total number
of responses
• Easy to draw
• The graph does not show percent
of responses of each category
• Can be difficult to read accurately
if the bars don’t end on a line
Line Graph
Jill's Weekly Deposit
500
400
300
200
100
0
Jill's Weekly Deposit
Week 1
Week 2
Week 3
Week 4
Line Graph
Advantages
Disadvantages
• Easy to read and draw
• Can be used to estimate values
between points
• Can be used to show “trend”
• Best used to show information
over time
• Sometimes hard to read when data
is not on grid lines
• Does not show percent of whole