Pie Graphs, BarColumn Graphs and XY Scatter Plots

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Pie Graphs, Bar/Column Graphs and X-Y Scatter
Plots
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A multiple column/bar graph is
used to show comparisons between two categories.
In this case it is types of crime and the year.
It is still important to know the whole to which
the percentages refer.
It is clear here that the whole is all crime
since violent crime (73) property crime
(27) all crime (100)
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Arranging the data for a multiple column/bar
chart
A second set of categories
A blank space
Select all of this!
One set of categories
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II. x-y scatter plots

• An x-y scatter plot is a way of graphing data
  that changes over time
• In this class, virtually all of the x-y scatter
  plots you look at will be something that changes
  over time (abortion rate, population, poverty
  line, the price of stamps, etc.).
• So, the x-axis will be years, and the y-axis will
  be the quantity that is changing.
• When possible, use relative rather than absolute
  numbers.
• When labeling the x and y-axis and giving the
  chart a title, make sure you know the units and
  the whole to which percents (if you are using
  percents) refer.

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Here are the violent crime statistics (in
thousands) for the United States since 1990
Why is this NOT a very interesting graph?
These are absolute numbers. We dont know what
these numbers mean relative to the population of
the U.S..
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To fix the problem, get the population for each
of these years
Note All data is in thousands
and then compute total crimes/total population
to get the crime rate.
For example in 1990, (1,820 thousand
crimes)/(249,470 thousand people) .00703 OR
703 crimes per 100,000 people
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How might we describe this graph using language?

• The crime rate is
• Increasing
• Leveling off
• Decreasing
• Leveling off
• Decreasing

• We might also notice when the highest and lowest
  points occurred
• In 1991-92 there were 758 crimes per 100,000
  people
• In 2003, there were 475 crimes per 100,000 people

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Putting this altogether, we could describe the
graph as follows
The goal in this sort of description is to 1.)
Give a good idea of overall trends, and 2.) Point
out the most interesting or surprising features.
In the early 90s crime rates were still rising in
the United States, but they peaked in 1992 at 758
crimes per 100,000 people. Through the mid to
late 90s there was a decline in the crime rate,
bringing it to a low-point of 475 crimes per
100,000 people in 2003. But, we may have some
cause for concern because although the crime rate
has continued to decrease, it seems to have
leveled off after the turn of the millennium.
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A Pie Chart is. . . . used to show categories
that dont overlaplike percents of a whole!
We can easily tell that the largest percent of
women saved came from first class
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Some Pie Chart Advice

• Never include the Total Category!
• Never use categories that overlap!
• Do use a Pie Chart for a single-frame snapshot of
  your topic pie charts dont track changes over
  time.
• The total of all the categories should sum to 100

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Finally, what do you think about this graph?
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Good luck!