Graphing and Introduction to Statistics

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Graphing and Introduction to Statistics
Chapter Eight
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Reading Pictographs, Bar Graphs, Histograms, and
Line Graphs
Section 8.1
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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.
  An advantage of using a pictograph to display
  information is that comparisons can easily be
  made. A disadvantage of using a pictograph is
  that it is often hard to tell what fractional
  part of a symbol is shown.

Martin-Gay, Prealgebra, 5ed
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The pictograph shows the approximate number of
passengers traveling on the leading U.S.
passenger airlines.
Source Air Transport Association of America 1998
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Bar Graphs

• Bar graphs can appear with vertical bars or
  horizontal bars. An advantage to using bar graphs
  is that a scale is usually included for greater
  accuracy.

Martin-Gay, Prealgebra, 5ed
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Bar Graphs
The bar graph shows the population of the worlds
largest cities.
Source United Nations, Dept. for Economic and
Social Information and Policy Analysis
Martin-Gay, Prealgebra, 5ed
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Histograms

• A histogram is a special bar graph. The width 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 occurred and is called the class
  frequency. The bars in a histogram lie side by
  side with no space between them.

Martin-Gay, Prealgebra, 5ed
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Histograms

40-49 1
50-59 3
60-69 2
70-79 10
80-89 12
90-99 8
Student Scores
Frequency ( of students)
The test scores of 36 students are summarized in
the table.
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Line Graphs

• Another common way to display information
  graphically is by using a line graph. An
  advantage of a line graph is that it can be used
  to visualize relationships between two
  quantities. A line graph can also be very useful
  in showing change over time.

Martin-Gay, Prealgebra, 5ed
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Line Graphs
Tornado Deaths
Source Storm Prediction Center