CREATE TABLE table_29155 ("No. in series" FLOAT, "No. in season" FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Original air date" TEXT, "U.S. viewers  ( million ) " TEXT)

How many episodes were written by Alison McDonald?
SELECT COUNT("Directed by") FROM table_29155 WHERE "Written by" = 'Alison McDonald'
SELECT COUNT("Directed by") FROM "table_29155" WHERE "Written by" = 'Alison McDonald'