The Bar Graph or Bar Chart

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The Bar Graph or Bar Chart

• What is it? How to Draw it

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What is a Bar Graph?

• A bar graph is a graph that displays the
  frequency or numerical distribution of a
  categorical variable, showing values for each bar
  next to each other for easy comparison.
• Alternate Name
• Bar Chart

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Bar Graph Example

• In June 2005, the US Dept of Transportation
  reported the following data by observing 1700
  motorcyclists nationwide at randomly selected
  roadway location
• Proper Helmet 731
• Insufficient Helmet 153
• No Helmet 816
• Total 1,700

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Vertical Bar Graph Example
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x-axis y-axis Variables

• On a vertical bar graph, the y-axis variable is
  normally a quantitative variable.
• Is it discrete or continuous?
• On a vertical bar graph, the x-axis variable is
  normally a categorical variable

Categorical Variable
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Type of Variables on the Previous Motorcycle Bar
Graph

• x-axis?
• Categorical Variable.
• Name the categories
• Proper, Insufficient, None
• y-axis
• Discrete Quantitative Variable
• What are the units?
• Helmets

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Making a Bar Graph Look Better

• What would make this bar graph look better?
• If we ranked the numbers by either increasing or
  decreasing value, the appearance would be less
  jagged, making a Pareto Chart.
• What is a Pareto Chart?
• A bar graph in which the bars are ordered
  according to value, in either increasing or
  decreasing order.
• Why Pareto Charts? Graph is named for Vilfredo
  Pareto, an Italian mathematician economist.
  1848-1923.

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Vertical Bar Graph as Pareto Chart
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Education Annual Income Survey
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Retail Sales
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Pareto Chart of Sales At Retail Outlets
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Non Pareto Version of Sales
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Bar Graphs VERY FLEXIBLE FORMAT

• Advantage over Pie Charts
• Bar Graphs are easier to make to read than pie
  charts.
• How are they similar to Pie Charts?
• Both pie charts bar graphs can display the
  distribution of a categorical variable
• How are they different from Pie Charts?
• A bar graph can also compare any set of
  quantities measured in the same units.

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Psychic Phenomena
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Pareto Chart of Psychic Phenomena
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In Class SurveyDo you believe in Supernatural
Phenomena?
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In Class SurveyDo you believe in Supernatural
Phenomena?
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In Class Survey Results from 2009Do you believe
in Supernatural Phenomena?
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In Class Survey Results from 20093-Level
Comparative Bar Graph
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In Class Survey Results from 2009 Simple Bar
Graph
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In Class Survey Results from 2009 Pie Chart
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Rainfall In Hawaii
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Bar Graph Characteristics

1. Data can be quantitative or categorical
2. Bars can be vertical or horizontal
3. The x-axis represents the category displayed
4. The y-axis represents the quantitative values of
   the variable being displayed
5. Bars are of uniform width and uniformly spaced

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Bar Graph Characteristics

1. A consistent measurement scale is used for each
   vertical bar
2. Height of bars represent the values of the
   variable displayed, the frequency of occurrence
   or percentage of occurrence
3. The graph is well-annotated with title, labels
   for each bar, vertical scale, horizontal
   categories, source

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Changing Scale The Squiggle

• What is a squiggle?
• At least a 2-angle line on a bar graph axis that
  abbreviates a scale.
• When do you use a squiggle?
• Use a squiggle on the changed axis whenever you
  change scale in a bar graph.
• Horizontal Squiggle Vertical Squiggle

or
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Pie to Bar Spending On NY Lottery
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Spending On NY Lottery
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Spending On NY Lottery
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Turning a Pie Chart into a Bar Graph
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Turning a Pie Chart into a Bar Graph
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Turning a Pie Chart into a Bar Graph
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Turning a Pie Chart into a Bar Graph
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Would The Bar Graph Make a Good Pie Chart?

• Only when Bar Graphs represent parts of a whole,
  can it be made into a Pie Chart.
• If the answer is NO, you could write
• No, because these values are comparative data
  only.
• No, because these values DO NOT represent parts
  of the whole.
• If the answer is YES, you could write
• Yes, because these values represent parts of the
  whole.

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Bar Graph Pie Chart Relationship Summary

• Every Pie Chart COULD be made into a Bar Graph
• BUT
• NOT all Bar Graphs CAN be made into Pie Charts
• Pie Chart Þ Bar Graph
• Bar Graph Þ Pie Chart

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Turning a Pie Chart into a Bar Graph
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Turning a Pie Chart into a Bar Graph
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Turning a Pie Chart into a Bar Graph
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Turning a Pie Chart into a Bar Graph
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Turning a Pie Chart into a Bar Graph
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Turning a Pie Chart into a Bar Graph
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Turning a Pie Chart into a Bar Graph
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Turning a Pie Chart into a Bar Graph
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Deciding Which Graph is Better

• The Chicago Tribune polled 380 randomly selected
  Chicago residents from August 27 to 31, 2009 on
  the subject of the potential Chicago Olympics of
  2016.
• The question asked was, Do you favor or oppose
  Chicago hosting the 2016 Olympic games? The
  results of the poll were

• Supply the remainder of the data labels

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Could the Pie Chart Become a Bar Graph?

• The answer is obviously yes,
• But the question remains,
• Which Graph looks better? Which Graph is better
  for display purposes?
• This is a matter of opinion

• Supply the remainder of the data labels

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Examining a Bar Chart for Meaning

• Whats the question?
• Whats the title?
• Whats the population?
• Whats the sample?
• How many variables?
• What are they?
• Whats the conclusion?
• Good pie chart?
• Is this a Pareto chart?

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Turning a Pie Chart into a Bar Graph
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Turning a Pie Chart into a Bar Graph
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Turning a Pie Chart into a Bar Graph
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Turning a Pie Chart into a Bar Graph
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Turning Pie Charts to Bar Graphs
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Turning Pie Charts to Bar Graphs
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Turning Pie Charts to Bar Graphs
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Turning Pie Charts to Bar Graphs
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Turning Pie Charts to Bar Graphs
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Turning Pie Charts to Bar Graphs
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Turning Pie Charts to Bar Graphs
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Turning Pie Charts to Usual Bar Graphs
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Turning Pie Charts to Pareto Bar Graphs
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Steps in Bar Chart Construction

1. Use a straight edge on a piece of graph paper
2. Make a first-quadrant x-y axis, unless some of
   your data is negative
3. Examine the data and determine the maximum value
   of the quantitative data. Your y-scale must be at
   least this high

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Steps in Bar Chart Construction

1. Choose an appropriate scale for the y-axis.
2. Mark scale ticks consistently label them, until
   you reach a mark greater than the highest value
   of data.
3. Mark of the bar width of each piece of
   categorical data you will be using on the x-axis.

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Steps in Bar Chart Construction

1. Make sure you place a space between each of the
   data bars.
2. Plot each data point by drawing a bar of the
   correct width height for each.
3. Label the top of each bar with a value.
4. Label both x- and y-axes with a title
5. Title the graph
6. Label the source of the data.

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What Comes After High School?
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Pareto Chart of Path After Graduation
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Kids Borrowing Money (Replace)
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Mountains to Climb
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Quiz 103 Bar Charts

• Hints
• Complete the Vocabulary
• Then do the front page
• Place your HW in the HW box

You need Pencil, Eraser Calculator Graph Paper
(for 2 graphs one sheet okay) No bags on
desk Clear all lists in Calculator