What is the average Attendance, when Date is 1 October 1998?
CREATE TABLE "uefa_cup_winners_cup" (
  "date" text,
  "round" text,
  "opponent" text,
  "venue" text,
  "result" text,
  "attendance" real
);
SELECT AVG("attendance") FROM "uefa_cup_winners_cup" WHERE "date"='1 october 1998';