user: Question: What is the average crowd size when North Melbourne is the away 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: ['Footscray', '8.9 (57)', 'Hawthorn', '8.8 (56)', 'Western Oval', 9000.0, '7 June 1930']
SQL:

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