CREATE TABLE "round_17" (
  "home_team" text,
  "home_team_score" text,
  "away_team" text,
  "away_team_score" text,
  "venue" text,
  "crowd" real,
  "date" text
);

Question: What was the attendance when St Kilda played as the away team?
SQL: SELECT AVG("crowd") FROM "round_17" WHERE "away_team"='st kilda';