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Topic: A "plausible range" for a random variable
Replies: 9   Last Post: Jun 11, 2013 7:42 PM

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Posts: 60
Registered: 12/7/12
Re: A "plausible range" for a random variable
Posted: Jun 8, 2013 7:10 PM
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On 07/06/2013 19:31, Rich Ulrich wrote:
> Poisson consideration gives a good approximation for small
> proportions. This is applied for your N=2000, 2 1/2%, as follows.
> Rank 50 is the point estimate of L. The +/- 2SD range for Poisson
> can be estimated as ( Square(Sqrt(L) - 1), Square(Sqrt(L) + 1) )
> The square root of 50 is about 7; the square of 6 is 36, and the
> square of 8 is 64. That gives (approximately) the CI for L=50
> is (37, 65).

When the sample is taken in N(0,1), using your limits for N= 2000 I get
a 73% confidence level. Is that the intended level?

That CI doesn't seem good for other distributions (uniform, exponential,
log-normal and weibull), because I get 0 or 100%. Am I wrong?


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