Stats 1/25/2013

Big N little n What begins with those?
Nine new neckties and a nightshirt and a nose.

Big N = Population.    Little n = sample.

(n-1) explained:

http://sinairv.wordpress.com/2011/08/21/sample-variance-vs-population-variance-bessels-correction/

And if you are really bored at night:

http://en.wikipedia.org/wiki/Bessel's_correction

http://en.wikipedia.org/wiki/Friedrich_Bessel

Dividing standard deviation by the mean is the coefficient of variation.  Great for analyzing variation between populations. 

Standard Error of the Mean (SEM) = 

**(n-1) again for samples.**

Standard error is what is typically used instead of standard deviations.  As such, error bars in graphs are typically calculated using the standard error.  

Kurtosis:

Next week!!  Hypothesis testing and the assumption of our distributions.

http://mathworld.wolfram.com/HypothesisTesting.html