user: Question: What is the average crowd size when Collingwood 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: ['Hawthorn', '7.14 (56)', 'South Melbourne', '11.15 (81)', 'Glenferrie Oval', 20000.0, '15 April 1961']
SQL:

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