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Reading Pictographs, Bar

Graphs, Histograms, and Line Graphs

Section 8.1

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Reading Pictographs

A pictograph is a graph in which pictures or symbols are used. This type of graph contains a key that explains the meaning of the symbol used.

Advantage – comparisons can easily be made

Disadvantage – hard to tell what fractional part of a symbol is shown

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ExampleThe following pictograph shows the approximate number of spaceflights by various countries or space consortia for lunar or planetary explorations from 1957 to the present day. Use the graph to answer the questions.

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Slide 4Copyright © 2015, 2011, 2008 Pearson Education, Inc.

Examplea. Approximate the number of space flights by the United States.

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b. Approximate how many more spaceflights were undertaken by the USSR/Russia than by the United States

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Exampleb. Approximate how many more spaceflights were undertaken by the USSR/Russia than by the United States

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Reading and Constructing Bar Graphs

A bar graph can appear with vertical bars or horizontal bars.

Advantage – the scale is usually included for great accuracy.

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ExampleThe following bar graphs shows the number of endangered species in the United States in 2013. Use the graph to answer the questions.

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Examplea. Approximate the number of endangered species that are snails.

b. Which category has the most endangered species?

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Small Group ClassWork

Draw a vertical bar graph using the information in the table about electoral votes for selected states.

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Texas California Florida Nebraska Indiana Georgia0

10

20

30

40

50

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Slide 12Copyright © 2015, 2011, 2008 Pearson Education, Inc.

Reading and Constructing Histograms

A histogram is a special bar graph. The with of each bar represents a range of numbers called a class interval. The height of each bar corresponds to how many times a number in the class interval occurs and is called class frequency. The bars in a histogram lie side by side with no space between them.

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Reading Line Graphs

Another common way to display information with a graph is by using a line graph.

Advantage – it can be used to visualize relationships between two quantities. It can also show a change over time.

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Example

The following line graph shows the average daily temperature for each month for Omaha, Nebraska. Use the graph to answer the questions.

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Example

a. During which month is the average daily temperature the highest?

b. During what month, from July through December, is the average daily temperature 65 F?

c. During what months is the average daily temperature less than 30 F?