which test can i do to satisfy that inferred data is OK

#1
I have three parameters{MC, TVS and VC} which have a relationship between them. these parameters were measured from a pit latrine in Botswana. i have measured{MC and TVS} from a pit latrine in my country and want to determine VC from the other relationship. Which statistical method or tool or technique can i use to satisfy myself that the VC obtained using the relationship is close to the true VC in my country?
 
#2
What exactly are these variables you measured? MC, TVS and VC? It will be tough to approximate and make any conclusions about a variable from a different population that we don't have any samples on.
 
#3
What exactly are these variables you measured? MC, TVS and VC? It will be tough to approximate and make any conclusions about a variable from a different population that we don't have any samples on.
its MC- moisture content, TVS- total volatile Solids and viscosity, i have data for both population{in my country and Botswana}