Descriptive Statistics

• descriptive statistics


  the use of graphs, tables and summary statistics to identify general trends and patterns in a data set
• measures of central tendency


  a descriptive statistic that provides information about an 'average' value for a data set, (median and mode)
• mean


  the arithmetic average of a data set that takes the exact values of data into account
• median


  the middle value of a data set when the items are placed in rank order (from lowest to highest)
• mode


  the most frequently occurring value or item in a data set
• measures of dispersion


  a descriptive statistic that provides information about how spread out a set of data are (range and standard deviation)
• range


  the difference between the highest and lowest item in a data set, usually 1 is added as a mathematical correction
• standard deviation


  assesses the spread of data around the mean by telling us how much scores deviate from the mean
• mean strength


  most sensitive measure of central tendency- takes account of exact distance between all the values of all the data
• mean weakness


  easily distorted by extreme values= misrepresentative of the data as a whole
• median strengths


  -not affected by extreme scores

  -easy to calculate
• median weakness


  less sensitive than the mean- not all items included in the final calculation
• mode strength


  more useful for nominal (or categorical) data
• mode weakness


  not always representative of the whole data
• range strength


  easy to calculate
• range weakness


  only takes into account the two most extreme values- fails to take into account the whole distribution of the numbers
• standard deviation strength


  a precise measure of dispersion- takes all the exact values into account
• standard deviation weakness


  can be distorted by extreme values