Calculating Uncertainty for Standard Deviation

  • Thread starter Thread starter hellothere123
  • Start date Start date
  • Tags Tags
    Uncertainty
AI Thread Summary
To calculate the uncertainty of the standard deviation from multiple trials, the sample standard deviation is divided by the square root of the number of trials (N). However, this method pertains to the uncertainty in the measured value, not directly in the standard deviation itself. The uncertainty of the standard deviation can be derived from its relationship with the chi-square distribution, but specific methods for this calculation are not clearly defined in the discussion. There is uncertainty regarding whether the teacher's template was intended for this calculation. Overall, while it is possible to find the uncertainty of the standard deviation, the exact approach remains unclear.
hellothere123
Messages
30
Reaction score
0
My teacher is quite lazy and gave us a template. we are suppose to show our values and the estimates. but in the table there is a row for the standard deviations and we are suppose to put the best value +- the uncertainty. now he must have copied and pasted this for all the rows. Is there a way to find the uncertainty of the standard deviation that was found for like 10 trials? I don't think he meant for us to find the uncertainty for the standard deviation, but if it can be done, how do i find it? thanks
 
Physics news on Phys.org
The uncertainty is the sample standard deviation, divided by √N. (N is the number of trials).

EDIT:
Wait, that is for the uncertainty in the measured value. Did you need that, or the uncertainty in the standard deviation itself? That one I'm not sure of.
 
yes how do i find the uncertainty of the standard deviation itself.

it could be a mistake on the teacher's part, but i just wanted to know if finding the uncertainty for the standard deviation was possible.
 
I'm pretty sure it's possible, and that the sample standard deviation follows a chi-square probability distribution. Sorry I can't help with the details.
 
I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
Thread 'A cylinder connected to a hanging mass'
Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
Back
Top