user: Question: What is the average Attendance, when the Date is September 17, 1981?
Columns: ['Week', 'Date', 'Opponent', 'Result', 'Attendance']
Types: ['real', 'text', 'text', 'text', 'real']
Sample row: [1.0, 'September 6, 1981', 'at New York Giants', 'W 24–10', 72459.0]
SQL:

assistant: SELECT AVG("Attendance") FROM "Table" WHERE "Date" = 'September 17, 1981';