Descriptive Statistics

• What are descriptive statistics?

  a way of summarising quantitative data & patterns, inform us of the central value in a data set
• What are the 3 measures of central tendency?

  mean, median, mode
• mean


  add all the values, divide by the amount of values
• Strengths of the mean


  Most sensitive measure of central tendency because it takes account of all values in data set
• Limitations of the mean


  Easily distorted by extreme values
• Mode


  most common value in a set of data
• strength of the mode


  • unaffected by extreme scores
  • ideal for nominal data
• limitations of the mode


  • doesn't take all values into consideration
  • data can have more than one mode or no mode
• Median


  The central value in a set of data when it is ordered from lowest to highest value.
• strengths of median


  • easy to calculate
  • unaffected by extreme values
• limitations of the median


  doesn't take all values into account
• measures of dispersion


  refers to how spread out the data is
• What are the two measures of dispersion?

  range and standard deviation
• range


  the difference between the highest and lowest scores in a distribution
• strengths of the range


  • easy to calculate
  • takes extreme values into consideration
• limitations of the range

  only using two values from the whole set of data
• standard deviation


  a computed measure of how much scores vary around the mean score
• What does a low standard deviation mean?


  Data points are close to the mean, participants gave similar answers
• what does high standard deviation imply?


  data is spread over a large range of values, not all participants were affected by the IV in the same way
• Strengths of standard deviation


  takes all the data points into account
• limitations of standard deviation

  hard to calculate