MATHS

• lower quartile range


  (N+1) divided by 4
• higher quartile range


  3 ( N + 1) divided by 4
• why is standard deviation useful?


  • not affected by extreme values
  • useful for measuring and assessing the degree of variability or spread of data in geography field
  • good measure of reliability of mean value - a data set with less extreme values has a more reliable mean
• disadvantages of standard deviation 


  • it doesn't give the full range of data - need to calculate the range
  • can be hard to calculate - errors can occur if done by hand so spreadsheet is needed
  • considers all data points equally , can be impacted by extreme values or outliners - distort data and not give accurate image