Descriptive statistics

• Measure of central tendency

  'Averages' which give us information about the most typical values in a set of data: mean, median, mode
• Mean

  Calculated by adding up all the scores/values in a data set and dividing this figure by the total sum of scores there are
• Strengths to mean

  Most sensitive measure of central tendency because it takes account of all values in data set meaning it is more representative of the data as a whole
• Weakness to mean

  Easily distorted by extreme values doesn't really represent the data overall
• Median


  Middle value in a data set when scores arranged from lowest to highest
• Strengths to median

  Extreme scores do not affect it and easy to calculate
• Weakness to median

  Less sensitive than mean as not all scores included in final calculations
• Mode


  Most frequently occurring score/value within a data set. When there are two modes, it is a bi-modal
• Strength to mode

  Easy to calculate
• Weakness to mode

  Very crude (simple) measure
• Measure of dispersion

  Based on the spread of scores: how far scores vary and differ from one another
• Range

  Calculation of the spread of scores and worked out by taking lowest value from the highest value- usually adding one
• Strength to range

  Easy to calculate
• Weakness to range

  Only take into account the 2 most extreme values and may be unrepresentative of the data set as a whole
• Standard deviation

  Much more sophisticated measure of dispersion. Single value that tells us how far scores deviate from the mean.
• Strength to standard deviation

  More precise than the range includes all values within a calculations, therefore there is a more accurate picture of an overall distribution of data set
• Weakness to standard deviation

  Can be distorted by a single extreme value like the mean