Fagerström (1982) studied the effect of using nicotine gum as an adjunct to a standard program for giving up smoking. One group received the standard psychological treatment program normally employed by Fagerström's clinic. A second group received the same program but was also supplied with gum containing nicotine, which they were instructed to chew when they felt the need to smoke. Each group contained 50 participants, and participants were classified as abstinent or not at one month and at six months. How should he analyze his data? What problem arises from the fact that there was not a group given plain-old- candy-store gum? (Note: The experimental [gum] group had abstinence rates of 90% and 64% at one and six months, respectively, and the control group had rates of 60% and 45%.)