user: Question: What is the average crowd size when the home team is North Melbourne?
Columns: ['Home team', 'Home team score', 'Away team', 'Away team score', 'Venue', 'Crowd', 'Date']
Types: ['text', 'text', 'text', 'text', 'text', 'real', 'text']
Sample row: ['St Kilda', '8.5 (53)', 'South Melbourne', '11.16 (82)', 'Junction Oval', 10150.0, '6 August 1955']
SQL:

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