[R] variance of discrete uniform distribution

[Rolf Turner]

On 9/03/2010, at 12:13 PM, casperyc wrote:

> 
> Hi all,
> 
> I am REALLY confused with the variance right now.

	You need to learn the difference

		(a) Between sample variance (*estimate* of population variance) and
		    population variance.

	and

		(b) Between discrete and continuous distributions.


	Given that you understand those differences you will see that all three
	answers are correct.

		cheers,

			Rolf Turner
> 
> for a discrete uniform distribution on [1,12]
> 
> the mean is (1+12)/2=6.5
> which is ok.
> 
> y=1:12
> mean(y)
> 
> then var(y) 
> gives me 13
> 
> 1- on  http://en.wikipedia.org/wiki/Uniform_distribution_%28discrete%29 wiki 
>    the variance is (12^2-1)/12=143/12
> 
> 2- 
> http://www.solvemymath.com/online_math_calculator/statistics/continuous_distributions/uniform/param_uniform.php

	***LOOK*** at the above.  Does it or does it not contain the string
	``continuous_distributions''???  And doesn't your question involve
	the ***discrete*** uniform distribution???

			R. T.
> here 
>    which used (12-1)^2/12=121/12
> 
> all different 3 answers!!!
> 
> All I am looking for is the variance of a random variable from discrete
> uniform distribution.
> 
> Can someone clearify that for me please?
> 
> Thanks.

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