ISP 120 Week 3

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ISP 120 Week 3

• Making and Interpreting Graphs

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Assignment 1 - 1
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2
4
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• x 2008, y 19.3684

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• x 1953, y 43.7169
• y 100, x 1825.86 1825

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Activity 2 - 1

• Suppose a magic genie gives you a choice. He
  will give you 1000 each day in the month of
  March or he will give you .01 on March 1st, .02
  on March 2nd, .04 on March 3rd, doubling the
  amount each day.
• http//qrc.depaul.edu/Excel_Files/Genie.xls

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2

• Determine if each of the following tables
  represents a relationship that is linear or
  exponential.
• Linear relationships have a constant RATE OF
  CHANGE
• Exponential relationships have a constant PERCENT
  CHANGE
• http//qrc.depaul.edu/Excel_Files/Linear_Exponenti
  al.xls

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3

• a.  Percentage Increase  The Lexus, LX470 costs
  24 more than the Mercedes, ML500.  If the price
  of the Mercedes, ML500 is 54,530, what is the
  price of the Lexus, LX470?
• N 54530(1.24) 67,617.20
• b.  Percentage Decrease  A department store
  advertises jeans for 30 off the original price. 
  If the original price of the jeans is 60, what
  is the sales price?
• N 60(1-.3) 42.00

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• c.  Percentage Increase    On August 12, 2005,
  one share of Lucent stock cost 2.95.  On
  September 8, 2005, the stock closed 7.8 higher. 
  What was the cost of one share of Lucent stock on
  September 8th?
• N 2.95(1.078) 3.18
• d.  Percentage Decrease  Sue went on a weight
  loss program an lost 10 of her weight.  If Sue
  weighed 150 pounds prior to her weight loss, what
  did she weigh after her weight loss?
• N 150(1-.1) 135 lbs
• e.  Percentage Increase    If the population of
  the state of Illinois is 104 larger than the
  population of Indiana in 2000, what was the
  population of Illinois if the population of
  Indiana was approximately 6,080,000?
• N 6,080,000(11.04) 12,403,200 people

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4

• The population of the Russia in 1998 was 147
  million the population of Nigeria was 106
  million.  Russia is decreasing in population by
  approximately 0.1 annually the population of
  Nigeria is growing at 3.  Using Excel, predict
  the year when Nigeria's population will exceed
  Russia's, assuming that the current trend
  continues.  How much faith do you have in your
  answer? What factors could affect the validity of
  your prediction?
• http//qrc.depaul.edu/acadieu/Winter2007/Activitie
  s/activity2-4.xls

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5

• Will go over next week some groups did not
  finish number 5

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Radioactive Decay - Example

• A radioactive substance decays 3.5 every
  decade.  How many years will it take for there to
  be only 40 of the original 100 of the substance
  to be left?
• Here the original value is 100 and the decay
  rate is 3.5 or .035 in decimal form.  Y
  represents the percent of the substance remaining
  and x represents the number of decades that have
  passed. 

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• 40 100 (1-.035)x
• .40 .965x
• log (.40) log (.965)x
• log (.40) x log (.965)
• x log (.40)/log(.965)
• x   25.71887
• This means that is will take about 25.719 decades
  or 257.19 years for there to be only 40
  remaining.   

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Week 3 Overview

• Graphing
• Pie Charts
• Percentage Of
• Bar Charts
• XY Graphs
• Effective Graphs
• Worksheet 3
• Activity 4

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Pie Charts
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Making a Pie Chart

• Make sure you select the categories and the
  values
• Make a descriptive title
• Sometimes it may be necessary to show one or two
  decimal places (the default is zero decimal
  places)
• http//qrc.depaul.edu/Excel_Files/EnergyConsumptio
  n.xls

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Percentage Of

• Coal 20.94 Quadrillion BTU
• Total Energy Consumption 93.82 Quadrillion BTU
• Percentage of Coal Use

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When to use Pie Charts

• 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
• Variable energy
• Categories coal, petroleum, natural gas, etc.
• The categories must be disjoint
• Do not include the totals on the pie chart
• Add percentage data labels

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Bar Charts
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Making a Bar Chart

• Note that a graph with one data series does not
  need a legend delete it!
• A legend is ABSOLUTELY necessary when graphing
  multiple series make sure you label them!
• Go to Source Data and type the name of the series
  in the name input box for each series
• http//qrc.depaul.edu/Excel_Files/HomeHeating.xls

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Not Needed!!
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MUST HAVE!!
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When to use Bar Charts

• Bar charts are very flexible
• They can be used whenever quantitative data is
  associated with categorical variable
• Great with a limited amount of data or when you
  want to compare more than one series
• Make sure the years are consecutive if you have
  years along the x-axis

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More on using Bar Charts

• Advantage succinctness allows for easy
  comparison within categories and across
  categories
• Best used in printed works so that viewers can
  study them carefully
• Disadvantage sometimes represent too much data
  and it takes a long time to absorb the data

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Problem with Bar Charts

• If you are trying to make a bar graph with
  quantitative data for the x-axis, Excel will
  interpret those values as quantitative data for
  the y-axis
• One way to correct this is to only select the
  quantitative data you want to graph before you
  start creating the graph
• When you are on step 2 of the wizard, click on
  the series tab and select the box by Category (X)
  axis labels
• Highlight the categories and hit Enter
• http//qrc.depaul.edu/Excel_Files/HomeHeating.xls

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XY Graphs
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Making XY Charts

• Same graphs we made in week 1
• Make sure to select the XY Scatter with data
  points connected by lines
• http//qrc.depaul.edu/Excel_Files/LakeMichiganLeve
  ls1988-2000.xls

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When to Use XY Graphs

• Should be used when you have a lot of data
  points and the categories along the x-axis are
  numerical
• For example, measuring water levels over time
• We use the XY scatter graphs instead of the Line
  graphs in Excel (line graphs always treat the
  x-axis categorically instead of numerically)

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Story of an XY Graph

• What is the graph telling an audience
• With XY graphs, you must be able to write
  paragraphs which carefully describe what the
  graph is saying about the context
• Generally when telling the story of a graph, we
  traverse from left to right

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Some Concepts to Consider

• Increasing positive slope
• Decreasing negative slope
• Valleys and Peaks (mins and maxs)
• A periodic function is a function that repeats
  its y-values after some definite period has been
  added to the x-value

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An Example

• The water level of the lakes were not constant
  over the years. They started decreasing from
  1998 1990. The levels began to gradually
  increase from 1990 1993 when there was a slight
  decrease until 1995. The level then increased
  until it peaked in 1997. Then the water level
  began a rapid decrease until 2000. In 1990, the
  water levels were the shallowest recorded until
  2000 where it is recorded at the all-time low.

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Creating EFFECTIVE Graphs

• Address the following items each time you make a
  graph
• What is the purpose of making a graph from this
  data?
• What type of graph should you make?
• Decide on a title and consider the Ws (who,
  what, when, where)
• Descriptive x-axis label (if applicable)
• Descriptive y-axis label (if applicable)
• Is this an appropriate scale (if applicable)?
• Include the source (if possible) in a text box on
  the graph

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An Effective Graph Should

• Be able to stand alone without any words to tell
  the reader what they are looking at
• Be understood without a story or caption

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Misleading/Faulty Graphs

• Data can be graphed correctly but give
  different messages depending how it is displayed
• Y-axis scale effects
• Most common way graphs can be misleading
• More and more accepted in the media to adjust the
  y-axis

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Bad Graphs in the Media

• What is wrong, misleading, or biased about the
  following graph?

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• There are no labels on the axes.  The only way to
  tell what is measured on the y-axis is if you
  notice the sign next to the Hollywood Casino
  value. 
• The graph is misleading in that the y-axis scale
  (92.5 to 94) was chosen to overemphasize the
  differences in the heights of the columns.  If
  the correct scale (0 to 100) was chosen, the
  differences between the heights would not be very
  noticeable.  This was done to imply that
  Hollywood Casinos payout percentage is much
  higher than the other casinos payouts. 
• Also the Hollywood Casinos column extends beyond
  the boundaries of the graph.  This is done to
  mislead the reader into thinking that their
  Casino is better than the others. 

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What is wrong, misleading, or biased about the
following graph?
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• The scale on the x axis is inconsistent.  It
  starts increasing by 1 year but the last interval
  is 6 years.  This is not allowed. 
• The misleading impression is that the large
  increase in receipts happened in a short period
  of time, but in reality the growth took 6 years. 
  
• It the scale on the axis had been space
  correctly, the growth would appear much more
  gradual. 

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What is wrong, misleading, or biased about the
following graph?
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• Pie graphs can only be used if the data
  represents a meaningful total and there are no
  overlapping categories. 
• This data contains overlapping categories.  Each
  member of the population can be categorized by
  race AND by gender. 
• It is incorrect to put all this data on one pie
  graph.  2 pie graphs should have been used.