What is the mean number of events when top-5 is 1?
CREATE TABLE "summary" (
  "tournament" text,
  "wins" real,
  "top_5" real,
  "top_10" real,
  "top_25" real,
  "events" real,
  "cuts_made" real
);
SELECT AVG("events") FROM "summary" WHERE "top_5"=1;