CREATE TABLE table_62383 ("Week" FLOAT, "Date" TEXT, "Opponent" TEXT, "Result" TEXT, "Attendance" FLOAT)

What was the attendance on September 11, 1988?
SELECT AVG("Attendance") FROM table_62383 WHERE "Date" = 'september 11, 1988'
SELECT AVG("Attendance") FROM "table_62383" WHERE "Date" = 'september 11, 1988'