1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Calculating moments in MS Excel

  1. Sep 8, 2007 #1

    As part of a school project on statistics, I'm trying to calculate some parameters of collected data. I've the marks of 50 randomly sampled students in 6 subjects. I'm trying to calculate their skewness. Since the inbuilt Excel function to calculate skewness uses an estimator I've never seen, I'm using the standard estimator:

    [tex]\frac {\sqrt{n (n-1)}}{n (n-2)} \frac {\Sigma_i (x_i - \bar{x})^3}{s^3}[/tex]

    Though this is not unbiased, it's the best I have as I can not assume normality (which is creating a load of problems) because the population is heavily (-)vely skewed .

    In Excel, I've written the following formula:

    =(SQRT($A51*($A51-1))/(($A51-2)*$A51))*(SUM((D2:D51 - D53)^3)/POWER(D55,3))

    where D2:D51 contains the data, $A51 is n, D53 is the mean and D55 is the sd.

    Is this correct? It seems a pity Excel has no in-built functions to calculate moments. Also, one of the values is coming out to be -1.099, and I can't remember whether odd-order standardized moments can be less than -1 :redface:

    Thanks for your help. This is really important or me.

  2. jcsd
  3. Sep 8, 2007 #2


    User Avatar
    Science Advisor
    Homework Helper

    From Excel help:

    If you have to use your formula, all you have to do is to multiply Excel's result with [tex]\frac {\sqrt{n (n-1)}}{n (n-2)}\times \frac{(n-1)(n-2)}{n}. [/tex]
    Last edited: Sep 8, 2007
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook