Re: [ai-geostats] F and T-test for samples drawn from the same population

2004-12-05 Thread Digby Millikan
I believe a related topic is called the proportional effect, which is displayed when populations display related, but different properties, as discussed in Geostatistical Ore Reserve Estimation, M. David, pp170, which also displays itself in a sudy of the normal and relative variograms. Regards

Re: [ai-geostats] F and T-test for samples drawn from the same p

2004-12-05 Thread Digby Millikan
Every resource model I have done, I always subdivide the populations into those of equal mean and variance, so stationarity is obeyed, is this the correct procedure, I havn't read Mining Geostatisitcs in detail yet, but understood that this was a basic requirement for geostatisitical modelling pro

Re: [ai-geostats] F and T-test for samples drawn from the same p

2004-12-05 Thread Digby Millikan
Colin, Isn't a basic rule of geostatisitics that all populations must follow the intrinsic hypothesis, i.e. stationarity ,constant mean and variance, so you should split any populations that do not have the same mean and variance, introduced pp33 Mining Geostatistics A.G.Journel & Ch. J.Huijbregts.

[ai-geostats] Large samples, t tests, etc

2004-12-05 Thread myers
Most of the tests of hypotheses that have been mentioned recently on this list serv are non-spatial, i.e., there is nothing in the underlying statistical assumptions that specifically pertains to spatial data. The one common assumption is "random sampling" or "iid" (independent, identically distr

RE: [ai-geostats]F and T-test for samples drawn from the same p

2004-12-05 Thread Mat (University Account)
Sorry if this is somewhat off subject - but I'd like to discuss (and invite further comments) on Colin's comments regarding the effects of independence on standard statistical tests. He mentioned that a lack of independence "typically removes a large part of the usability of basic tests unless c

RE: [ai-geostats] F and T-test for samples drawn from the same p

2004-12-05 Thread Pierre Goovaerts
Hello, I am currently principal investigator on a major NIH grant that aims to develop software for test of hypothesis using alternate hypothesis specified by the user and that differ from the omnibus "spatial independence"; we called them "spatial neutral models". For example, you can test for cl

[ai-geostats] RE: F and T-test for samples drawn from the same p

2004-12-05 Thread Isobel Clark
Hence my recommendation to use cross cross validation Isobel http://geoecosse.bizland.com/books.htm --- Colin Daly <[EMAIL PROTECTED]> wrote: > > > Hi > > Sorry to repeat myself - but the samples are not > independent. Independance is a fundamental > assumption of these types of tests - an

RE: [ai-geostats] F and T-test for samples drawn from the same p

2004-12-05 Thread Colin Daly
Title: RE: [ai-geostats] F and T-test for samples drawn from the same p Hi Sorry to repeat myself - but the samples are not independent.  Independance is a fundamental assumption of these types of tests - and you cannot interpret the tests if this assumption is violated.  In the situation w

Re: [ai-geostats] F and T-test for samples drawn from the same p

2004-12-05 Thread Chaosheng Zhang
Dear all,   I'm wondering if sample size (number of samples, n) is playing a role here.   Since Colin is using Excel to analyse several thousand samples, I have checked the functions of t-tests in Excel. In the Data Analysis Tools help, a function is provided for "t-Test: Two-Sample