CREATE TABLE "round_15" (
  "home_team" text,
  "home_team_score" text,
  "away_team" text,
  "away_team_score" text,
  "venue" text,
  "crowd" real,
  "date" text
);

Question: What was the average crowd size when Melbourne was the home team?
SQL: SELECT AVG("crowd") FROM "round_15" WHERE "home_team"='melbourne';

Question: What was North Melbourne's score when they were the home team?
SQL: SELECT "away_team_score" FROM "round_15" WHERE "away_team"='north melbourne';