Variance

[bekib86]

Hi, ive got a statistics question in an exam on wednesday. Im doing nursing and have printed off a handout from my uni which states that the variance is the sum of all the values minus the mean squared and then divided by n-1 (Variance = Σ(x - mean)� / n-1)
However, from doing maths A level and looking on the internet, i always have thought it was just divided by n not n-1?
Can anyone explain this to me why it is n-1
Thanks
Beki

[corinth748]

http://davidmlane.com/hyperstat/A16252.html
does this help?
regards