user: Question: What was the average crowd size when Melbourne was the home team?
Columns: ['Home team', 'Home team score', 'Away team', 'Away team score', 'Venue', 'Crowd', 'Date']
Types: ['text', 'text', 'text', 'text', 'text', 'real', 'text']
Sample row: ['Melbourne', '15.17 (107)', 'North Melbourne', '6.14 (50)', 'MCG', 8421.0, '10 August 1929']
SQL:

assistant: SELECT AVG("Crowd") FROM "Table" WHERE "Home team" = 'Melbourne';