## Re: AI-GEOSTATS: bounds of IK variograms

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• Jorg, that is correct. The variance of any binary variable (such as an indicator variable, 0s and 1s) is, by definition, p*(1-p), where p is the percentile
Message 1 of 3 , Jun 16, 2003
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Jorg, that is correct.

The variance of any binary variable (such as an indicator variable, 0s and 1s) is, by definition, p*(1-p), where "p" is the percentile of the distribution.

Therefore, the maximum possible variance of an indicator variable will be 0.25, when p=0.5; also, the variance as a function of the percentiles is a symmetrical curve, where p=10 has the same variance as p=90.

The only comment is, that, strictly speaking and as you probably know, covariances and variograms are not always interchangeable.

Cheers,

Mario

"Dilling,_J�rg" <Joerg.Dilling@...> wrote:
dear all,

i have performed indicator kriging with different thresholds (corresponding
to 10th percentiles). is it correct that the variogram of each
xth-percentile is bounded to:

max cov = xth_percentile* (1-xth_percentile) ??

e.g. max cov (30th perc.) = 0.21, max.cov (90th perc.) = 0.09

regards
j�rg

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Dipl. Geo�kologe J�rg Dilling
Bayerisches Geologisches Landesamt
- Au�enstelle Marktredwitz -
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D - 95615 Markredwitz

Tel.: ++49 (0)9231 - 951 105
Fax.: ++49 (0)9231 - 951 102
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