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# Double Line Graphs

## Drawing two line graphs on the same grid to compare related data

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Double Line Graphs
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## Double Line Graphs

### Topic

Election Poll Data

### Vocabulary

• Double Line Graphs
• Double Broken-Line Graphs

### Student Exploration

#### How do politicians and voters use Double Line Graphs during election?

During government election time there are a lot of people whose careers are dedicated solely toward collecting voters’ opinions on a variety of different issues related to elections. Often times this data is presented in graphs, and many times in a double broken-line graph to compare poll data for different candidates running for one government position.

Check out the following double broken-line graphs for the 2012 United States presidential election! What can you conclude based on the graphs?

Use the graph to answer the following questions.

1. Who would you predict to win the election? What information from the graph brings you to that conclusion? Explain.
2. When was the election the closest? How close were the voters’ opinions of the two candidates?
3. When in the election did the voters favor one candidate much more than the other? How far divided were voters’ opinions of the two candidates?
4. When did voters’ opinion of Romney grow the most? When did voters’ opinion of Obama grow the most?
5. When did votes’ opinion of Romney decline the most? When did votes’ opinion of Obama decline the most?

Use the graph to answer the following questions.

6. Describe Obama’s favorability. What information from the graph brings you to that conclusion? Explain.
7. When was Obama’s favorable rating the highest? When was Obama’s unfavorable rating the lowest? How do these two ratings correspond? Explain.
8. When was Obama’s unfavorable rating the highest? When was Obama’s favorable rating the lowest? How do these two ratings correspond? Explain.
9. When did Obama’s favorable rating grow the most? When did Obama’s unfavorable rating grow the least? How do these two ratings correspond? Explain.
10. What is the benefit of presenting Obama’s favorability as a double broken-line graph? Do you think it would be more beneficial to present it in another form? Explain.

### Extension Investigation

Beyond double line graphs there are triple, quadruple, etc. line graphs. Examine the following triple broken-line graph representing how voters in the United States identified with the three major political parties in the 2012 election.

11. Describe the trends in the populations’ identification with the political parties. Be sure to refer to specific values on the graph.
12. When is the number of people who identify with the Independent party the highest?
When is the number of people who identify with the Democrat party the highest?
When is the number of people who identify with the Republican party the highest?
13. When is the number of people who identify with the Independent party the lowest?
When is the number of people who identify with the Democrat party the lowest?
When is the number of people who identify with the Republican party the lowest?
14. What is the benefit of presenting Party Identification as a triple broken-line graph?
Do you think it would be more beneficial to present it in another form? Explain.

Further extension.

15. How can a double line graph help you compare the trend of rises and falls of two different companies' stock? How can this help you make an informed decision?

### Connections to other CK-12 Subject Areas

• Basic Graph Types
• Broken-Line Graphs

### Notes/Highlights Having trouble? Report an issue.

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