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carolynt
New Member

USA
2 Posts

 Posted - 09/25/2007 :  09:54:26 I have been trying to prove that one form of the equation for sample variance,x-((x)n) = (x-mean), another form of the same equation.So far, given the definition of mean being xn , I now have x-((x)n) = (x-((x)n))I have been looking online and have not found what to do after this step. Is there a way to separate the right half of the equation into the two parts separated by the subtraction on the left side? Or how can you change the n that is on the right side into the n present on the left?

tkhunny

USA
1001 Posts

 Posted - 09/25/2007 :  10:40:42 It may help to know the specific words "Machine Formula".http://www.bls.gov/ore/pdf/st990210.pdfhttp://www.cba.uh.edu/peixoto/DISC6360/s_mean.PDFhttp://faculty.washington.edu/conquest/482fall02/HW/hw1solution.htmAlso, please check your notation. You appear to have some exponents in the wrong places.

carolynt
New Member

USA
2 Posts

 Posted - 09/26/2007 :  06:37:54 You were right, the equation is x-((x)n)= (x-mean)I finally found the proof. It is basically working with the principle that mean=(x)n. Also, that mean and x = nmean and nx, respectively. You can factor the (x-mean) into a trinomial, then, by reworking the two last factors using the definitions above, combine the second and third terms because they are like terms.Thank you so much for your help and the website links!
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