Estimated is the opposite of Actual. Actual is the opposite of Theoretical. Theoretical is related to Ideal. Ideal is the opposite of Filter. 
Stranger is related to Foreign. Foreign is similar to International. International is derived from National. Citizen is a type of National. 
Estimated <--Antonym--> Actual <--Antonym--> Theoretical <--RelatedTo--> Ideal <--Antonym--> Filter 
Stranger <--RelatedTo--> Foreign <--SimilarTo--> International --DerivedFrom--> National <--IsA-- Citizen 