CREATE TABLE table_3938 ("No. in series" FLOAT, "No. in season" FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Original air date" TEXT, "Production code" FLOAT, "U.S. viewers  ( millions ) " TEXT)

how many millions of North American people saw the episode whose director was Ed Sherin?
SELECT "U.S. viewers (millions)" FROM table_3938 WHERE "Directed by" = 'Ed Sherin'
SELECT "U.S. viewers (millions)" FROM "table_3938" WHERE "Directed by" = 'Ed Sherin'