On 04-Dec-09 07:18 AM, yogesh karpate wrote: > @ Pauli and @ Colin: > Sorry for the late reply. I was busy > in some other assignments. > # As far as normalization by(n) is concerned then its common > assumption that the population is normally distributed and population > size is fairly large enough to fit the normal distribution. But this > standard deviation, when applied to a small population, tends to be > too low therefore it is called as biased. > # The correction known as bessel correction is there for small sample > size std. deviation. i.e. normalization by (n-1). > # In "electrical-and-electronic-measurements-and-instrumentation" by > A.K. Sawhney . In 1st chapter of the book "Fundamentals of > Meausrements " . Its shown that for N=16 the std. deviation > normalization was (n-1)=15 > # While I was learning statistics in my course Instructor would advise > to take n=20 for normalization by (n-1) > # Probability and statistics by Schuam Series is good reading. > Regards > ~ymk > > > > Yogesh,
Thanks for the Bessel name, I hadn't come across that before. The Wikipedia reference for the Bessel Correction uses a divisor of n-1: http://en.wikipedia.org/wiki/Bessel%27s_correction Perhaps the simplification for larger n comes from the fact that for large n, 1/n => 1/(n-1). I would suggest C. E. Weatherburn - Mathematical Statistics, but I doubt whether it is still widely available. Colin W. _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
