measures of central tendency and dispersion

• Measures of central tendency

  Any measure which calculates an average value within a set of data
• Mean


  Arithmetic average, total of all values in a set of data is divided by the number of values
• Strengths of mean

  • Makes use of all values
  • Good for interval data
• Limitations of mean

  • It is influenced by outliers (extreme scores) so it can be unrepresentative
• Median


  Arrange data from lowest to highest then find the central value
• Strengths of median

  • Not affected by extreme scores
  • Good for ordinal data
• Limitations of median

  • Not as sensitive as mean, does not use all data
• Mode


  The most frequently occurring value in a set of data
• Strengths of mode


  • Useful for nominal data (data in categories)
• Limitations of mode


  • Is not useful when there are several modes
• Measures of dispersion


  Any measure that calculates the variation in a set of data
• Range


  Minus the lowest score from the highest score
• Strengths of range

  • Easy to calculate
• Limitations of range

  • Affected by extreme values
  • Does not use all data
• Standard Deviation (SD)


  The square root of the variance calculates SD. A low SD means that more data is clustered close to the mean hence there is less data spread
• Strengths of SD

  • Precise measure where all data values are taken into account
• Limitations of SD

  • Difficult to calculate
  • Affected by extreme values
• Standard Deviation (SD)


  • The square root of the variance calculates SD
  • A low SD means that more data is clustered close to the mean hence there is less data spread
• Standard Deviation (SD)


  • Precise measure where all data values are taken into account
  • Difficult to calculate
  • Affected by extreme values
• Standard Deviation (SD) does not use all data
• Standard Deviation (SD) is affected by extreme values
• Measures of central tendency indicate the approximate center of a distribution, such as the mean, median, and mode
•  Measures of dispersion describe the spread of the data, such as the range, upper and lower quartiles, variance, and standard deviation
• these measures help to summarize and analyze the data