Table schema:
CREATE TABLE table_name_38 (area__km_2__ INTEGER, name VARCHAR, population__2011_ VARCHAR)

Question: For Stellenbosch, which has a population larger than 155,733, what is the average area?
SQL: SELECT AVG(area__km_2__) FROM table_name_38 WHERE name = "stellenbosch" AND population__2011_ > 155 OFFSET 733