user: Question: What was the average size of the crowd for matches held at Corio Oval?
Columns: ['Home team', 'Home team score', 'Away team', 'Away team score', 'Venue', 'Crowd', 'Date']
Types: ['text', 'text', 'text', 'text', 'text', 'real', 'text']
Sample row: ['Hawthorn', '7.9 (51)', 'St Kilda', '15.12 (102)', 'Glenferrie Oval', 12000.0, '20 July 1929']
SQL:

assistant: SELECT AVG("Crowd") FROM "Table" WHERE "Venue" = 'Corio Oval';