# Thread: Unbiased sample variance question

1. ## Unbiased sample variance question

I have what should be a very simple problem, however I'm sure the answer im getting is wrong =(

Calculate the unbiased sample variance of the following numbers (weights of bags of sugar, not that it makes a difference).

1013, 997, 1013, 1013, 1004, 985, 991, 997

I know the formula is

( 1 / (n-1) ) * Sum((xi-mean)^2)

So i plug in the numbers, and i get

mean = 1001.625

For Sum((xi-mean)^2) I get 825.875 (wrong?)

Then plugging in the values I end up with a variance of 117.98 which is clearly wrong, I think it should be 10.86ish.

Can anyone point out my (probably trivial) error please?