Re: AI-GEOSTATS: Re: generalize kriging variance to average-based estimators different than

[JW]

Hello Oriol,   Isobel gave good advice when she suggested to download Chapter 4 of her Practical Geostatistics. This book taught me more than David's Geostatistical Ore Reserve Estimation and Journel and Huijbregts's Mining Geostatistics combined because of its many practical examples. For example, look at Clark's hypothetical uranium data (see Clark and the Kriging Game at http://www.ai-geostats.org/documents/JW_Merks/ ) and find out what happens if the variance of the distance-weighted average were to resurface after it went missing on Krige's watch at the Witwatersrand gold reef complex in South Africa in the 1950s. You should  also peruse http://en.wikipedia.org/wiki/Geostatistics to find out why statistically astute thinking was lacking when pioneering geostatisticians replaced the genuine variance of a single distance-weighted average with the pseudo kriging variance of some set of kriged estimates.  Study Clark's hypothetical uranium data step-by-step as outlined on the Geostatistics talk page. It is possible to make the variance of the distance-weighted average vanish again by the condition that this variance be replaced with the kriging variance of some set of kriged estimates if, and only if, the absolute difference between the true variance and the Central Limit Theorem exceeds say 1% or perhaps 5%. Conditional switching between real variances and voodoo variances may not be a bright idea so early in your career.   Kind regards, Jan W Merks ----- Original Message ----- From: Isobel Clark To: Oriol Falivene Cc: ai-geostats@jrc.it Sent: Wednesday, July 12, 2006 6:06 AM Subject: AI-GEOSTATS: Re: generalize kriging variance to average-based estimators different than Oriol   Download for free, my old book Practical Geostatistics. Chapter 4 tells you all about calculating the variance for any weighted average estimator.   Follow links from http://www.kriging.com   Isobel Oriol Falivene <[EMAIL PROTECTED]> wrote: Dear Colleagues, I’m a PhD student working on interpolation of categorical variables (like facies). I would like to know if it’s possible to generalize the kriging variance to other average-based estimators different than kriging, such as kriging with an areal trend, indicator kriging or inverse distance weighting?; if it’s possible could you send me some references where I can find that?. Thank you. Best regards Oriol -- ______________________________________ Oriol Falivene [EMAIL PROTECTED] http://www.ub.es/ggac tel. (+34) 93 4034028 fax (+34) 93 4021340 Fac. de Geologia, Univ. de Barcelona + + To post a message to the list, send it to ai-geostats@jrc.it + To unsubscribe, send email to majordomo@ jrc.it with no subject and "unsubscribe ai-geostats" in the message body. DO NOT SEND Subscribe/Unsubscribe requests to the list + As a general service to list users, please remember to post a summary of any useful responses to your questions. + Support to the forum can be found at http://www.ai-geostats.org/