user: Question: What is the average crowd size for Princes Park?
Columns: ['Home team', 'Home team score', 'Away team', 'Away team score', 'Venue', 'Crowd', 'Date']
Types: ['text', 'text', 'text', 'text', 'text', 'real', 'text']
Sample row: ['Fitzroy', '14.8 (92)', 'Melbourne', '17.18 (120)', 'Junction Oval', 12363.0, '1 May 1971']
SQL:

assistant: SELECT AVG("Crowd") FROM "Table" WHERE "Venue" = 'Princes Park';