The Student Room Group
Competition - post a photo you've taken of nature >>
Competition - post a photo you've taken of nature >>
Competition - post a photo you've taken of nature >>

S3 Edexcel Query

Hey,So in the Edexcel S3 book, chapter 3 examples 8 and 10, they're using this formula to calculate the estimated variance: (uploaded)

Why is the denominator (n-1) instead of n as usual? Am I missing something completely obvious?


Any help will be much appreciated thanks!
CodeCogsEqn.gif0.9KB
Reply 1
Avatar for TeeEm
TeeEm
19
Original post by Nikhilm
Hey,So in the Edexcel S3 book, chapter 3 examples 8 and 10, they're using this formula to calculate the estimated variance: (uploaded)

Why is the denominator (n-1) instead of n as usual? Am I missing something completely obvious?


Any help will be much appreciated thanks!


there are 2 different formulas

the one you are quoting is that of an unbiased estimator for the variance of a population, from a sample of n observations and it is denoted by s2
Original post by TeeEm
there are 2 different formulas

the one you are quoting is that of an unbiased estimator for the variance of a population, from a sample of n observations and it is denoted by s2


Thanks!

is there a proof of as to why it's 'n-1' instead of n?


Posted from TSR Mobile
(edited 8 years ago)
Reply 3
Avatar for TeeEm
TeeEm
19
Original post by Nikhilm
Where did they specify that in the book? They didn't quote it in bold as usual?


Posted from TSR Mobile


Where?
How will I know that ?

c11.jpg
Original post by TeeEm
Where?
How will I know that ?

c11.jpg


Lol I realised how stupid that reply was so I edited it but obviously not in time
Reply 5
Avatar for TeeEm
TeeEm
19
Original post by Nikhilm
Lol I realised how stupid that reply was so I edited it but obviously not in time


no worries ... it is late!

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you