The pitcher plant from Borneo, Nepenthes rafflesiana, has two kinds of pitchers, upper and lower, that it uses to trap and digest insects. The upper pitchers use fragrance to lure mainly flying insects. The lower pitchers trap mainly ants. Di Giusto et al. (2010) tested whether odors emitted by the lower pitchers were cues for ant attraction. In one experiment, they presented individual ants, Oecophylla smaragdina, with air from a bag containing a lower pitcher in one arm of a Y-tube. Humidified air was provided in the other arm as a control. In 14 of 19 independent trials, ants chose the arm containing the pitcher, whereas the remaining five ants chose the control arm. Do these data indicate a preference for one arm or the other? Use an exact test.