user: Question: What was the Average crowd when the away team was 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: ['Fitzroy', '14.12 (96)', 'North Melbourne', '15.15 (105)', 'Junction Oval', 10034.0, '5 July 1975']
SQL:

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