Descriptive Statistics

• what do measures of central tendency do?

  averages that give infomation on the most typical values in a set of data
• how do you calculate mean


  adding up all of the results and dividing the sum by the total number of results
• whats a + of mean


  it includes all the scores/values so is more representative than other methods
• whats a - of mean

  one very large or small can make the mean distorted
• how do you calculate median

  place number in order & determine middle number
• whats a + of median

  less affected by extreme scores
• whats a - of median

  less sensitive than the mean, not all scores are included
• whats the mode

  the most frequently occurring value in a set of data
• what is it called if there is 2 modes

  bi-modal
• whats a + of mode

  easy to calculate, but only possible if data measured is categorical
• whats a - of mode

  could be very different from mean & median - doesn't represent all the data
• whats the range

  the difference between the highest and lowest value
• whats a + of range

  easy to calculate
• whats a - of range

  can be distorted by extreme values, only takes into account the most extreme & not a fair spread of the scores
• what is the measure of dispersion

  based on the spread of scores - how far the scores vary from one another
• what is standard deviation


  measure telling you how far Ps deviated from the mean
• what does a larger SD mean


  the greater the dispersion
• what does a larger SD suggest

  not all PS affected by the IV in the same way
• what does a smaller SD mean

  data is tightly clustered around the mean
• what does a smaller SD suggest

  Ps responded in a similar way
• what is a + of SD

  much more precise than the range - includes all scores
• whats a - of SD

  can be distorted by extreme values but less distorted than the range
• what is preferred order of averages

  mean, median, mode
• what are the 3 measures of central tendency

  mean, mode, median
• what are the 2 measures of dispersion

  range and standard deviation