Statistics for Decision Making

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Statistics for Decision Making

• Descriptive Statistics Wrapping it Up

2
Comments about Homework

• Show your work!
• Chapter 1 stuff really important, but lets
  take a look again in 12 weeks
• Use pencil, not pen
• Staple multiple sheets together
• Units of measure this is not a math class (our
  numbers represent something!)
• Go beyond textbook answers make sense of the
  results
• Use appropriate level of precision high for
  intermediate results same as data for final
  figures

3
Frequency DistributionsDetermining Frequency
Groups

• Start by breaking the data range into k equal
  width intervals
• Let n represent the number of observations
• Number of intervals such that 2k gt n
• Interval width
• Start with (Max - Min) / k
• Use convenient breakpoints for intervals
• 91.0 through 97.4 (OK)
• 90.0 through 95.0 (Better)
• Intervals no overlap no gaps

4
Frequency DistributionsDetermining Frequencies

• Absolute frequencies
• Count number of observations in each interval
• Relative frequencies
• Divide absolute frequency by total number of
  observations
• Cumulative frequencies
• Add frequencies for all previous intervals (note
  difference from manner done in text)
• Cumulative relative frequencies
• Add relative frequencies for all previous
  intervals

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Histograms

• What are they?
• Just graphical displays of frequency
  distributions
• Absolute frequencies
• Relative frequencies
• Cumulative frequencies
• Provide picture of the variation in the data
• Basics
• Horizontal axis values for variable of concern
• Vertical axis indicates corresponding
  frequencies

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Miscellaneous Statistics

• Less important but need to be familiar with
• Location
• Median
• Mode
• Quantiles
• Variation
• Range
• Min and Max
• Both (?)
• Z-score
• Empirical Rule