Measures of

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• Measures of
• Central Tendency

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Measures of Central Tendency

• Mean the average score
• Median the value that lies in the middle after
  ranking all the scores
• Mode the most frequently occurring score

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Measures of Central Tendency

• Which measure of Central Tendency should be used?

• The measure you choose should give you a good
  indication of the typical score in the sample or
  population.

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Measures of Central Tendency

• Mean the average score is sensitive to
  extreme scores
• ex. 1 2 3 4 5 6 7 8 9 10
• Mean 5.5 (median 5.5)
• ex. 1 2 3 4 5 6 7 8 9 20
• Mean 6.5 (median 5.5)
• ex. 1 2 3 4 5 6 7 8 9 100
• Mean 14.5 (median 5.5)

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Measures of Central Tendency

• Median
• is not sensitive to extreme scores
• use it when you are unable to use the mean
  because of extreme scores

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Measures of Central Tendency

• Mode
• does not involve any calculation or ordering
  of data
• use it when you have categories (e.g.
  occupation)

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Variation or Spread of Distributions

• Range
• It compares the minimum score with the maximum
  score
• Max score Min score Range
• It is a crude indication of the spread of the
  scores because it does not tell us much about the
  shape of the distribution and how much the scores
  vary from the mean

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Variation or Spread

• Measures that indicate the spread of scores
• Range - the difference between the
• highest and lowest scores
• Ex. 2, 5, 9, 17, 8, 27, 1, 34
• Range 34 - 1 33

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Example

• Find the mean, median, mode, and range from the
  following set of data values
• 2, 4, 9, 13, 16, 22
• Mean-
• Median-
• Mode-
• Range-

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Example 2

• Find the mean, median, mode, and range from the
  following set of data values
• 60, 64, 69, 73, 76, 122
• Mean-
• Median-
• Mode-
• Range-
• What does the value of 122 do to the data set?

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How would the values change without 122?

• Find the mean, median, mode, and range from the
  following set of data values
• 60, 64, 69, 73, 76
• Mean-
• Median-
• Mode-
• Range-