CREATE TABLE table_74571 ("Home team" TEXT, "Home team score" TEXT, "Away team" TEXT, "Away team score" TEXT, "Venue" TEXT, "Crowd" FLOAT, "Date" TEXT)

What was the average crowd size of games held at Glenferrie Oval?
SELECT AVG("Crowd") FROM table_74571 WHERE "Venue" = 'glenferrie oval'
SELECT AVG("Crowd") FROM "table_74571" WHERE "Venue" = 'glenferrie oval'