ISP 120 Mathematical

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ISP 120 Mathematical Technological Literacy I

• September 25, 2007
• Benjamin Graham, MS, LCPC

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Agenda for Today

• In lecture
• Review Homework 1
• Overview of graphs
• In-class group activity
• In Computer Lab
• In-lab lecture on graphing with Excel
• Group Activity 4

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Types of graphs

• There are MANY!
• For this session, we will focus on three main
  types
• Pie Charts
• Line Graphs (X-Y graphs)
• Bar Charts

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Pie Charts

• Pie charts are very limited in their
  applicability.
• They can only be used when you have a
  quantitative variable associated with a list of
  categories where both the categories and the
  quantities each add up to a whole. The categories
  must also be disjointthey cannot overlap.

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Line Graphs (X-Y graphs)

• XY graphs (or line graphs) - xy graphs should be
  used when you have "a lot" of data points and the
  categories along the x-axis are numerical. 
• In Excel, choose the xy scatter type and then
  choose a graph option with connected data
  points.  
• Note what Excel calls a "line graph" is very
  confusing and should essentially never be used
  for our projects/activities. 

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Bar Charts

• Bar charts  - Finally I talk about bar charts,
  which are very flexible.  They can be used
  whenever there is a quantitative variable
  associated with the a categorical variable, and
  they can be even be used with a quantitative
  x-axis. They are great when you have a limited
  amount of data or when you what to compare more
  than one series.  (If you do use a bar chart and
  have years along the x-axis, be sure the years
  are consecutive.  Otherwise, you can be guilty of
  creating a miselading graph.)

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Whats wrong with this graph?
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Wrong with this graph?
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Lets look closer
1.8-1.5/1.5 20 change Visual image of 1.5
is ½ the size of visual image of 1.8 2-1/1
100 changenot accurate!
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Y-axis scale effects

• The previous and the following examples show the
  impact of Y-axis scale effects. This is
  something to be aware of when working with
  graphs.
• While changing the scale of the y-axis does not
  misrepresent the data (i.e., it doesnt lie),
  but it can grossly distort the conclusions your
  reader comes to by viewing the graph (i.e., a
  white lie).

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Whats wrong with this graph?
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Whats wrong with this graph?
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Graphing in Excel

• In-class demo