Histograms

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Histograms

• A Graphical Method for Describing Quantitative
  Data

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Mean SAT I Math Scores by State (2003)Data
Source The College Board, New York, NY
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Histogram Example (SAT Math Scores)
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Measurement Classes, Frequencies, and Relative
Frequencies for the SAT Math Scores
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Histogram Terminology

• Measurement Classes (or Bins)
• Frequency
• Relative Frequency
• Area of each rectangular region represents a
  probability
• Sum of all rectangular regions must equal one

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Frequency Versus Relative Frequency
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Histograms

• Histograms condense the data by grouping similar
  data values into the same class (bin) in the
  graph.
• Summarize Data
• Sort
• Min /Max
• Range (Max Min)
• Mean (Average values)
• Group
• Plot

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Histograms

• Go to www.math.arizona.edu/dsmith
• Open the data file for your team
• Compute the differences in arrival times and
  service times
• Determine the min, max, average and range
• Determine appropriate bins
• Create histograms of relative frequencies
• Use this to form a preliminary estimate of the
  number of ATMs that you would need during your
  two service periods

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Table 1. EPA Mileage Rating on 100 Cars
Source McClave, James T and Terry Sincich
(2003). Statistics, 9th Ed. Prentice Hall New
Jersey, pp. 30.