Crest White Strips were a great product innovation from Proctor & Gamble. Recently, P & G has observed that sales have been declining rapidly at approximately 4% per month. To do effective research to understand why this is happening, P & G should engage in consumer research among:
a) A convenience sample of current users
b) A probability sample of the target audience
c) A probability sample of previous users
d) A convenience sample of those interested in whiter teeth
e) A probability sample of those using alternate whiteners
