How many times was the episode named "conference call"?
CREATE TABLE "u_s_nielsen_ratings" (
  "num" real,
  "episode" text,
  "rating" text,
  "share" real,
  "rating_share_18_49" text,
  "viewers_millions" text,
  "rank_timeslot" real,
  "rank_night" real,
  "rank_week" text
);
SELECT COUNT("num") FROM "u_s_nielsen_ratings" WHERE "episode"='\"Conference Call\"';