Error Bars
Add error bars to your bar chart. The height of the error bars should be the standard error of the mean, SEM, of the values used to compute the bar height. Standard error of the mean can be computed with the equations:
\[\sigma = \sqrt{\frac{1}{n - 1} \sum_{i=1}^{n} (x_{i}-\bar{x})^2}\]
\[SEM = \frac{\sigma}{\sqrt{n}}\]
Where x1, x2, … xn are the values used to compute the bar height and \(\bar{x}\) is the average of the values.