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# Double Line Graphs

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# Double Line Graphs - Answer Key

## 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.

Answers will vary based on when the graphs are viewed. The sample answers to #1-5 are based on the snapshot graph below.

1. Who would you predict to win the election? What information from the graph brings you to that conclusion? Explain.
Based on this snap shot I would predict that Obama would win the election because the majority of the polls have predicted that so far at all points in the election. In addition, Obama is still ahead.
It could also be argued that Romney would win because in the most recent polls support for Obama has declined while support for Romney has increased. If this trend were to continue then support for Romney would bypass the support for Obama.
2. When was the election the closest? How close were the voters’ opinions of the two candidates?
The election is currently the closest it has been. There is less than 1% of a difference in the support of the two candidates, 46.0% of voters support Obama while 45.6% of voters support Romney. To be exact, there is a seperation of 0.4% in the support 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?
Voters favored Obama much more than Romney around February $12^{th}$ of 2012. 48.4% of voters supported Obama while 42.6% supported Romney.
4. When did voters’ opinion of Romney grow the most? When did voters’ opinion of Obama grow the most?
Voters’ opinion of Romney grew the most around July $11^{th}$, 2012. Voters’ opinion of Obama grew the most around January $14^{th}$, 2012.
5. When did votes’ opinion of Romney decline the most? When did votes’ opinion of Obama decline the most?
Voters’ opinion of Romney declined the most around January $14^{th}$, 2012. Voters’ opinion of Obama declined the most around April $24^{th}$, 2012.

Answers will vary based on when the graphs are viewed. The sample answers to #6-10 are based on the snapshot graph below.

Use the graph to answer the following questions.

6. Describe Obama’s favorability. What information from the graph brings you to that conclusion? Explain.
Overall Obama was the most favorable around December 2008 and January 2009, however since then his favorability has declined. This is seen with the downward slope of the navy blue favorable broken line and the upward slope of the red unfavorable broken line. Since June 2010, Obama’s favorability and unfavorability has remained relatively constant. You can see this in the graph with the red and navy blue lines being horizontal.
7. When was Obama’s favorable rating the highest? When was Obama’s unfavorable rating the lowest? How do these two ratings correspond? Explain.
Obama’s favorable rating was the highest on December $21^{st}$, 2008 with a rating of 70.4%. His unfavorable rating was at the same exact day with an unfavorable rating of 19.5%. It makes sense that they are at the same time because if people really favor him, there are less people to find him unfavorable.
8. When was Obama’s unfavorable rating the highest? When was Obama’s favorable rating the lowest? How do these two ratings correspond? Explain.
Obama’s unfavorable rating was the highest during the dates of August $27^{th}$ – October $9^{th}$, 2011. He had an unfavorable rating of 47.2% and his favorable rating ranged from 47.2%-47.4%. It is logical that they are at the same time because if a significantly high percentage of people found Obama unfavorable, then there were are less people to find him favorable.
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.
Obama’s favorable rating grew the most from September $28^{th}$ – December $21^{st}$ 2008. His unfavorable rating grew the least, declined the most, at this same time. Obama’s favorable rating grew and unfavorable rating grew the least at the same time.
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.
It is beneficial to see a candidate’s favorability as a double broken-line graph because you can see the trends in both his favorability and unfavorability and compare the two simultaneously. I think that it is most beneficial to see it in a double broken-line graph, but students might suggest other graphs (maybe with multiple pie charts for different times or with a double bar graph).

### 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.
Overall there has been a decline in the support of both the Democrat and Republican parties since October 2008, while there has been an increase in the amount of people that identify as Independents. In October 2008 there were more people that identified as Democrat and the smallest percentage of people identified as Republican. In July 2009 the percentage of people who identified as Independent surpassed the number of people who identified as Democrat. Since July 2009 the highest percentage of voters identify as Independent and the smallest percentage identify themselves as Republicans.
12. When is the number of people who identify with the Independent party the highest? January $24^{th}$, 2012 with 38.9%.
When is the number of people who identify with the Democrat party the highest? December $14^{th}$, 2008 with 37.5%.
When is the number of people who identify with the Republican party the highest? September $14^{th}$, 2008 with 27.9%.
13. When is the number of people who identify with the Independent party the lowest? September $11^{th}$, 2008 with 32.2%.
When is the number of people who identify with the Democrat party the lowest? January $31^{st}$, 2012 with 31.1%.
When is the number of people who identify with the Republican party the lowest? June $30^{th}$, 2012 with 23.7%.
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.
As there are two major political parties in the United States and then the third most common affiliation is “independent” it is very helpful to use a triple broken-line graph to represent the identification of voters. I think that it is most beneficial to see it in a triple broken-line graph, but students might suggest other graphs (maybe with multiple pie charts for different times or with a triple bar graph).

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?
With a double line graph you can track the value of two different companies’ stock over time, very easily. This could help you make a prediction of what will happen in the future with the stock, and decide which one to invest in.

### Connections to other CK-12 Subject Areas

• Basic Graph Types
• Broken-Line Graphs