Table schema:
CREATE TABLE table_name_16 (points INTEGER, year VARCHAR, entrant VARCHAR, chassis VARCHAR)

Question: What are the average points of Scuderia Scribante with a Brabham bt11 chassis before 1968?
SQL: SELECT AVG(points) FROM table_name_16 WHERE entrant = "scuderia scribante" AND chassis = "brabham bt11" AND year < 1968