Compare predict and experimental values

Hi everybody:
I just generate different maps of interpolation with different methods but 
with the same package -(gstat, i used the krige command). And now for 
evaluate the best method i want to compare the predict values versus 
experimental, but i don't know how do it.
Could anybody tell me how should do it?.
Thanks in advance.

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	   Antoni Vi??dez Mora	
    Dept. Din??mica de Contaminantes
	    Fundaci??n CEAM
        Paterna (Valencia)-Spain
        tel: 961318190. ext: 216
 e-mail: toni at ceam.es  viudez_ant at gva.es
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