## [ai-geostats] Biased sampling spatial relationship

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• Dear Experts To understand semivariograms in case of biased sampling, could you please explain me what is arithmetic mean of the first data points and
Message 1 of 2 , Jun 2, 2005
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Dear Experts
To understand semivariograms in case of biased sampling, could you please
explain me what is arithmetic mean of the first data points and arithmetic
mean of the second data points within data pairs for a particular lag
distance. ( I am reading the book: Applied Geostatistics for Reservoir
Characterization;Mohan Kelkar...,2002,page 68)
I need to know why they may be different. I was thinking if there are pairs
of data, either first point of the pair or second point of the pair will be
the same in number and if a sample could be the first point of the pair, it
would be the second also in another place of the calculation chain and the
mean of both first and second points in data pairs if we calculate them
separately show the same mean because they are at the end the same???

Very Best Regards
Reza Nazarian
• Reza; It might be true if you are working with regular data where the head of one pair will be the tail of the next pair. But even here the tail of the first
Message 2 of 2 , Jun 2, 2005
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Reza;

It might be true if you are working with regular data where the head of
one pair will be the tail of the next pair. But even here the tail of the
first pair in any row or column won't correspond to any other data value.
It is not definitely true for irregular data where there is no
organization here.

I would suggest to take a look at ch 4. of Isaaks and ...

Thanks
Abedini

On Thu, 2 Jun 2005, Reza Nazarian wrote:

>
> Dear Experts
> To understand semivariograms in case of biased sampling, could you please
> explain me what is arithmetic mean of the first data points and arithmetic
> mean of the second data points within data pairs for a particular lag
> distance. ( I am reading the book: Applied Geostatistics for Reservoir
> Characterization;Mohan Kelkar...,2002,page 68)
> I need to know why they may be different. I was thinking if there are pairs
> of data, either first point of the pair or second point of the pair will be
> the same in number and if a sample could be the first point of the pair, it
> would be the second also in another place of the calculation chain and the
> mean of both first and second points in data pairs if we calculate them
> separately show the same mean because they are at the end the same???
>