2.16. The BBC in Britain requested viewers to call the network and indicate their favorite poem. Of more than 7500 callers, more than twice as many voted for Rudyard Kipling's If than for any other poem. The BBC reported that this was the clear favorite.

(a) Explain what it means to call this a "volunteer sample."

(b) If the BBC truly wanted to determine Brits' favorite poem, how could it more reliably do so?