What is the average age of the visitors whose membership level is not higher than 4?
CREATE TABLE visitor (age INTEGER, Level_of_membership VARCHAR)
SELECT AVG(age) FROM visitor WHERE Level_of_membership <= 4
### Context: CREATE TABLE visitor (age INTEGER, Level_of_membership VARCHAR) ### Question: What is the average age of the visitors whose membership level is not higher than 4? ### Answer: SELECT AVG(age) FROM visitor WHERE Level_of_membership <= 4