1.  Graphs Math 8

2. Introduction to types of graphs  Graphs are pictures of data  They can help you communicate your ideas  We are going to identify advantages and disadvantages of different types of graphs

3. Before we graph: gather data  How many times did you use a vending machine last week? Number of times using vending machine Number of students 0 times5 1~4 times8 5~9 times4 10 or more times1

4. Pictograph 0 times 1~4 times 5~9 times 10+ times = 1 student

5. Pictograph Advantages of PictographDisadvantages 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

6. Circle Graph (pie chart)

7. Circle Graph AdvantagesDisadvantages 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

8. Bar Graph

9. AdvantagesDisadvantages 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

10. Line Graph

11. AdvantagesDisadvantages 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