Standard deviation from measures with different uncertainty

[player1_1_1]

Homework Statement

i have a few results of measurements, with different measurement uncertainty: L=5\pm0,2, L=5,1\pm0,1,L=5,2\pm0,3,L=5,3\pm0,1,L=5,4\pm0,2 and how can i count standard deviation and final result of measurement with uncertainty?

The Attempt at a Solution

i counted arithmetic mean, variance and standard deviation of all results, if they were the same I would just do this like this \Delta L=\sqrt{V(L)+U^2(L)} where U(L) is measurement uncertainty of a single result, but what to do when they are different?

 

[Stonebridge]

There's a good explanation of how to treat the uncertainty here
http://www.rit.edu/cos/uphysics/uncertainties/Uncertaintiespart1.html#estimate

 

[player1_1_1]

thanks for this link, it is very helpful, but there arent solution for what to do with this thing that i mentioned, do you have any other idea?