Line Plots and Histograms

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Line Plots and Histograms

• Similar but Different

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Line Plots

• Easy and visual way to organize data.
• consists of a horizontal number line,
• each value marked by an x over the corresponding
  value on the number line.
• The number of x's above each number indicates how
  many times each number occurred.

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Watch! Dont write yet!Data Set58, 30, 37,
36, 34, 49, 35, 40, 47, 47, 39, 54, 47, 48, 54,
50, 35, 40, 38, 47, 48, 34, 40, 46, 49, 47, 35,
48, 47, 46First put them in numerical
order.30, 34, 34, 35, 35, 35, 36, 37, 38, 39,
40, 40, 40, 46, 46, 47, 47, 47, 47, 47, 47, 48,
48, 48, 49, 49, 50, 54, 54, 58
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Now create your graph.

• Find the range of the Data and decide what
  increments would best show the data.
• It would be silly to make a graph in increments
  of one.
• It would be unnecessary to make the graph go to
  100.

• 30 35 40 45 50
  55 60

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Add the Data

• Place an X over the number as it appears in your
  data set

30, 34, 34, 35, 35, 35, 36, 37, 38, 39, 40, 40,
40, 46, 46, 47, 47, 47, 47, 47, 47, 48, 48, 48,
49, 49, 50, 54, 54, 58
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So What?

• The Line Plot allows us to see some trends more
  clearly.
• Outliers - data points whose values are
  significantly larger or smaller than other
  values.
• Clusters - isolated groups of points
• Gaps - large spaces between points

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• Which are Outliers?
• Which are Clusters?
• Where are Gaps?

30 and 58 34-35 and 46-50 Between 40 and
46 Between 50 and 54
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Try it !

• Data Set
• 30,36, 74, 36, 77, 80 36, 45, 36, 36, 37, 38, 38,
  50, 38, 39, 42, 42, 45, 45, 45, 45, 45, 48, 36,
  50, 50, 51,52, 38, 52, 74, 77,

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Put in Numerical Order

• 30,36, 36, 36, 36, 36, 36, 37, 38,38, 38, 38, 39,
  42, 42, 45, 45, 45, 45, 45, 45, 48, 50, 50, 50,
  51,52, 52, 74, 74, 77, 77,80
• Make a Number Line and Plot

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30,36, 36, 36, 36, 36, 36, 37, 38,38, 38, 38, 39,
42, 42, 45, 45, 45, 45, 45, 45, 48, 50, 50, 50,
51,52, 52, 74, 74, 77, 77,80
30 35 40 45 50 55 60
65 70 75 80
Fill in the xs in your notes. Its too hard to
do it in a PowerPoint!
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Histogram

• FREQUENCY is the key
• Measure Frequency of data
• Like a bar graph but measures the number of times
  the data occurs.
• Think of a Connect Four game.
• Every time a number is in the data, you drop a
  checker in the game.

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Bar Graph or Histogram?
This is a histogram of how many employees make a
certain amount of money. Every time there is
another employee in a salary category, the
histogram gets taller.
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Bar Graphs
The y axis is showing Dollars not Frequency.
This is not a histogram.
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Bar Graph or Histogram

• We want to compare total revenues of five
  different companies.

Bar graph. Key question What is the revenue for
each company?
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Bar Graph or Histogram

• We have measured revenues of several companies.
  We want to compare numbers of companies that make
  from 0 to 10,000 from 10,000 to 20,000 from
  20,000 to 30,000 and so on.

Histogram. Key question How many companies are
there in each class of revenues?
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Try One

• Data for the age of kids going on the
  merry-go-round.
• 2,3,10,5,3,7,9,4,4,10,6,3,4,8,10,