standard deviation

• definition

  spread of data around the mean
• advantage of using over the range

  shows the spread of data around the mean instead of just the difference between the highest and lowest values

  range include anomalies whereas standard deviation reduces their effect

  shows whether the difference between results is significant
• proving without a stat test

  if you add and minus the standard deviation from the mean to create error bars

  repeat for each value

  and there is an overlap between the highest and lowest of each values then it is likely that there is a significant difference