# What is the meaning of RMS?

I know it is root mean square.
For example a,b,c,d,e,f
RMS=sqrt((aa+bb+cc+dd+ee+ff)/6)
Is it right?

If you mean the RMS defined in an histogram, it is the standard deviation,
not the root mean square,

[quote=â€śmonetaâ€ť]If you mean the RMS defined in an histogram, it is the standard deviation,
not the root mean square,

see root.cern.ch/root/html/TH1.html#TH1:GetRMS[/quote]
I find RMS in Users_Guide_5_12.pdf
see root.cern.ch/root/doc/RootDoc.html
page 57.Statistics Display:
the root mean square (RMS)
IS it right?

could you tell me all the meaning of â€śthe 7 statistic displayâ€ť in my plot?
thanks!
i fit the histogramm with gaus

As I said before, the meaning of RMS is standard deviation. This is common in physics, as it is mentioned also in

mathworld.wolfram.com/Root-Mean-Square.html

I agree, we should indicate that clearly also in the User guide.

Concerning the picture:

Mean: Average of the histogram entries
RMS: Standard deviation of the histogram entries
Chi2: Chi2 value obtained from the fit :
Sum squares of the normalized residuals :

``````           Sum [( bin content - function value)/binError]^2
``````

ndf : number of degree of freedom in the fit =
number of bins used in calculating the chi2 - number of fit parameters

then we have the fitted parameters :

Constant: is the amplitude of the fitted Gaussian function
Mean : is the mean of the gaussian
sigma: standard deviation of the gaussian

In case of perfect gaussian data and infinite statistics RMS -> sigma

I hope it is clear,

Regards,

Lorenzo

2 Likes

[quote=â€śmonetaâ€ť]As I said before, the meaning of RMS is standard deviation. This is common in physics, as it is mentioned also in

mathworld.wolfram.com/Root-Mean-Square.html

I agree, we should indicate that clearly also in the User guide.

Concerning the picture:

Mean: Average of the histogram entries
RMS: Standard deviation of the histogram entries
Chi2: Chi2 value obtained from the fit :
Sum squares of the normalized residuals :

``````           Sum [( bin content - function value)/binError]^2
``````

ndf : number of degree of freedom in the fit =
number of bins used in calculating the chi2 - number of fit parameters

then we have the fitted parameters :

Constant: is the amplitude of the fitted Gaussian function
Mean : is the mean of the gaussian
sigma: standard deviation of the gaussian

In case of perfect gaussian data and infinite statistics RMS -> sigma

I hope it is clear,

Regards,

Lorenzo[/quote]
Yout are kind to me!
Thanks !
I am a student of China.And my professor did no know the meaning of RMS ,so i have to learn of them.So i tell him!
Wish you best!
Do you know Chinese?