How Do You Calculate the Average Error in Measurements?

[lauralovesyou]

Hi,

I was just wondering how you calculate the average error, is there a certain formula?

Ex:

Three landing distances were measured and they were

6.93 cm +/- 0.05cm
6.56 cm +/- 0.05cm
6.65 cm +/- 0.05cm

To calculate error, do you add the landing distances then divide them by three and then add the errors for each one, therefore the average would be 6.71cm +/- 0.2cm (actual is 0.15cm however error is always in one significant figure) or do you divide the averages by three also, therefore get 6.71cm +/- 0.05cm?

 

[Mapes]

This may help: http://en.wikipedia.org/wiki/Propagation_of_uncertainty#Example_formulas"