I plotted an error bar in standard deviation mode in excel with following data
[7, 6.9, 9.5, 14.5, 18.2, 21.5, 25.2, 26.5, 23.3, 18.3, 13.9, 9.6 ]
It plots the graph shown in below image
It looks like the error bar is drawn based on the mean (average) value of all data points.
Error bars are a graphical representation of the variability of data and are used on graphs to indicate the error, or uncertainty in a reported measurement. They give a general idea of how precise a measurement is, or conversely, how far from the reported value the true (error free) value might be.
Comparing the definition of error bar and the image something is odd. An error bar specifies how far correct value can exist from actual value. But attached image does not show that because error bar was not drawn from actual value
Please share your thoughts.