user: Question: When Fitzroy are the away team, what is the average crowd size?
Columns: ['Home team', 'Home team score', 'Away team', 'Away team score', 'Venue', 'Crowd', 'Date']
Types: ['text', 'text', 'text', 'text', 'text', 'real', 'text']
Sample row: ['Essendon', '20.15 (135)', 'Richmond', '11.12 (78)', 'Windy Hill', 24000.0, '12 August 1950']
SQL:

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